That users actually think about what they are doing.
As designers, we are focused on creating the best experiences for users, so we focus on the steps and interactions that users access to get things done. That attention to detail often makes us blind to the obvious: People just DO things, without the same type of focus we have. They open apps, access web sites, and figure things out in real time without paying much attention to “interaction models” or “information architecture.” Do you think there is a huge debate over the “hamburger menu” in user-land? Of course not.
Because we have such focus, we often overcomplicate matters, thinking that users will pay the same amount of attention that we as designers did. Nope. Their goals are not to learn a system, but to USE as system.
This is why leveraging existing patterns and testing designs with users is important. Many moons ago I spent a lot of time designing a financial management software app, and I thought I had created a brand new interaction paradigm. This was awesome, I thought. This was going to help people! Then I tested it, and people did not get it and also thought it was too complicated. A colleague, who really liked the work I had done, watched the user tests and complained about “stupid users.” I corrected him, saying that they were not the problem: The design was perfect for US, just not for the people it was intended.