Many reasons why this is hard. 1) UI design needs to be understood and implemented as a whole. This does not sound good for most of developers. I don't know why

Many reasons why this is hard. 1) UI design needs to be understood and implemented as a whole. This does not sound good for most of developers. I don't know why. 2) Of course, good UI designer (I wish I am) can create bite-sized chunks - divide UI plan into small parts that are more manageable from the development perspective. UI designer still has to be able to say what parts need to be there before the overall improvement is justified - in other words, when the resulting UI can be evaluated. 3) Developers have always an opinion what is good UI. Many features that make something very good to use for non-tech-people, or easy to learn, do not match into developer view of good UI. 4) Development environment tools, vocabulary and tools are not UI-designer friendly. 5) Dealing the above issues in daily work does not leave energy to have the same problems at free time.