Much of design theory is predicated on the belief that we humans are rational people making rational decisions in our best interests. The reality, though, is far from it. We are emotional creatures doing all sorts of crazy things.
Which is why one of my favorite videos on the importance of — and guidelines for — interface design is Will Dayble’s “The User is Drunk”. The original video from 2013 is less than 5 minutes long, and Dayble has also expanded it to a longer talk.
Will’s main point in the video is that we are not drunk, but we are distracted and busy and have a million more important things to worry about than the interface we’re using. In the last ten years we’ve come up with more elegant ways to describe the same thing, like “situational disability”, but the original point still holds: designing in a way that pretends that we’re not totally ourselves is a wonderful thing to do.