AFAIK UI was originally written with Qt4 and X. With libhybris they could not use either of those. It takes more than recompile to change it to Qt5 and Wayland. I'm looking at the big picture, not a single feature, and when there is huge amount of work to do, one has to prioritize. From that point of view it's not surprising that scalability of the UI was not in top priority instead of just getting it to work.