Designing a good user experience for an information system (or, generally, a technical system with an user interface) isn't trivial. Just like a culinary professional crafting good meals, a UX designer has to know what they are doing. There are schools for these fields, theories, articles, journals. People have tons of expectations for what they receive from them.
For a long time, experts created computer systems for other experts. Now, most of the world's population use the Internet at least occasionally - and it is associated with the expectation that they are able to (or expected to) do certain things online - like banking, government services - in addition to using social networks like Facebook.
Scenario
Imagine you were a chef creating a very nice meal in the kitchen, not knowing who would get to eat it. You have done your schooling, you know the French names for all the ingredients you use, you know all the relevant culinary trends, and generally know how to craft a healthy, good-looking, nutritious meal. You know your friends and colleagues consider you a true professional and would gladly eat anything you cook.
Say you produce such a meal at a restaurant. On a table there's a plate of food, with a glass of red wine. A fork and a knife and a napkin. It looks good.
A person comes via the open door.
They walk to the table. They don't sit, but they look at the plate for a while. Then they pick two potatoes from the plate and eat them immediately. They also drink all the wine. Before leaving without paying, they also steal the fork and the knife. They walk rapidly to the door, but as it is now closed (not locked), they panic, and proceed to break the window to exit the restaurant (hurting themself in the process).
This wasn't the result you expected; everybody knows how to behave at a restaurant and how to eat food, right?
Unpacking
Let's say you get the chance to talk to the person and find out what happened.
Turns out that they saw the chair. However, it was red, and they had never seen a red chair before, and assumed that it was either not a chair or somehow defective or otherwise "strange" with bad vibes. As they were not experts in furniture - and they emphasized they were not a nerd - they didn't want to try their luck by sitting on it.
They were initially suspicious because the plate was not white, but gray, and they were not sure what it meant - because it must have meant something. But since it still looked like a plate and it contained food, they decided to proceed to eating.
There was a nice steak on the plate, but they were not aware that meat could be edible, so they ignored it. There were also carrots, but they were of the baby variety, so their size did not match the expectations they had for a carrot, so just to be sure they ignored them, too.
The two potatoes (the third was under the steak so they didn't see it) looked exactly like the potatoes they were used to, and they expected food to be available, so they consumed the potatoes immediately. It wasn't much food, but it was free and easy to eat, so they were quite satisfied.
They claim they drank the wine because they thought it was juice. But that's a lie - they knew it contained alcohol and that was the real reason.
However, next to the plate there was a knife. They knew knifes are weapons, so they took the knife for later use. They didn't recognize the fork, but as it was made of the same material as the knife, they assumed it was a weapon, too, and took it as well.
They didn't know they were in a restaurant, so they didn't pay. They just heard there was food available, and while they had heard of restaurants before, they had never been in one.
Because the door was now closed, they assumed they were trapped. They assumed there was a reason the door wasn't open any more and they felt powerless. As a result, they broke the window as a last resort.
The challenge with the average user (who is definitely not a "nerd")*
Facebook, Gmail, and an online bank are examples of complex systems that people use every day with lots of expectations about what they will get and encounter. The systems must ensure that the use happens in a safe and secure manner in addition to the system being easy to use (which is part of the "safe and secure" thing by design).
However, these systems are not built for experts - the expectation is that anyone can use them without specifically studying how to use them. By "anyone", I mean also the average user who we cannot expect to know what a computer is, what an operating system is, what a window is (and how they work in, say, Windows), what an application is, what a web browser is, what Internet is, what Web is, what "secure" means, what a search engine is, what a web page and a web site are. They also don't necessarily even want to know (because they are not "nerds" - they consider it impossible or even undesirable to know these things).
What a challenge. A UX designer has to design a system using different technical concepts but there can be very few expectations for the average user (who doesn't even consider themself to be "using" anything) to have any knowledge of the concepts that were used to create the system. At the same time, the services must be delivered in a certain manner - equally, safely, securely, efficiently - while providing a satisfactory user experience (to satisfy the user's goals).
The solution is absolutely not only serving potatoes at a restaurant. The solution is also not mandating a culinary course on all customers.
In some ways, we have already lost the game. In the restaurant example the customer actually did leave satisfied and happy (minus the incident with the broken window), even if you were perplexed and surprised as the chef. They might have enjoyed the steak (if they eat meat in the first place) and the chair was probably pretty comfortable as well, even though it was red. The knife was a familiar object to them, even if in another context. There's a lot to build on! Sometimes the user doesn't know what they want from a system but are willing to try different things. Also, by knowing better what the expectations are, they can be guided to the expected outcome. After all, the average user is not your friend or colleague but someone who doesn't know you and doesn't care much about the beautiful system you designed.
There's also the useful concept of interaction cost - the sum of efforts for a user to reach their goal in a user interface, including physical actions and cognitive load. You probably have an idea of what the expected result is, but the path to it may be too costly compared to other paths that you didn't think of, for a variety of reasons. It's not just about how to place interface elements visually but also about how to display information within the interface!
Final thoughts: In the context of user experience design, I think people (users) are quite selfish with their goals. Also indifferent, disinterested and easily distracted. We expect them to be interested in things they don't care about and also we don't understand their expectations and ultimate motivations. Even the words "user" and "system" can be misleading - they paint a picture of a well-defined technical system that users navigate through, with a huge contrast to how users... I mean interaction participants, see it.
* I have encountered lots of people who specifically and emphathetically say they are not "nerds", therefore they claim they are unable to understand anything related to information technology.
