Biggest challenge for UI Builders is that programming unfortunately has the accepted meaning of typing cryptic colorful ASCII text into an editor. Stuff that makes programming easy is mainly for users who don't know how to program.

Not that I think it should be that way, that's just the psychology of programmers. Of course many don't realize that or won't admit it.

Also some programmers really haven't got the idea of code reuse through components. They don't understand how useful it is. But sometimes it also is in the first category of something that makes programming too easy so they don't want to be associated with that because they want to be known as an engineer that does hard things.

Also, even though people sometimes try new things on purpose, they usually do most things just because a lot of people are already doing that. So even if someone likes your system unless they perceive it as being popular already they may not use it.