Well, there is only limited time for a limited number of programmers. Some people want better DR, others adaptivity (me, since 2012), a skin shader, fumefx, velocity RE, etc etc etc.. The Corona team obviously chose to serve the field first which has a broad user base and is most likely to finance the development for the next couple of month/years - which is archviz. Doing a bit of everything would probably have ended in "not useful for anything serious". Sure, some people would like to use fumefx for fireplaces, but that's a small percentage and there are workarounds (like cards). Some things like DR or SSS are probably more important for a bigger fraction of users.