It's subconscious, if you don't try to notice you wont, instead you will just stop using things or dislike using things without knowing why specifically - or more subtle still, you will not be as efficient in those programs... The UI is inbetween what you are trying to interact with, so if it doesn't quite work right then the emotions are going to be more subtle and hard to differentiate because it's not your main focus.

You are more likely to intuitively get this once you have some experience attempting to design effective UIs (and actually trying to care about it).