Because... You can copy the UI of the leader and problem solved.
There you have GIMP with an absolute nightmare UI to use, but people keep saying, just get used to it. On the other hand, a single developer, in javascript, made a copy of photoshop, and most people I know prefer to use that over GIMP...
Just copy the UI that works, if you can't research your own UI.
Because... You can copy the UI of the leader and problem solved.
There you have GIMP with an absolute nightmare UI to use, but people keep saying, just get used to it. On the other hand, a single developer, in javascript, made a copy of photoshop, and most people I know prefer to use that over GIMP...
Just copy the UI that works, if you can't research your own UI.