I think one of the reasons is that "we don't train people on how to make UIs". If you look at when UI is introduced in CS programs, its as a visual example for

I think one of the reasons is that "we don't train people on how to make UIs". If you look at when UI is introduced in CS programs, its as a visual example for Object Oriented Programming. However, its introduced and immediately moved over. The next time its used is only if the program has a specific course on UI development.