Most kids do not want to do that. And for the 1.8/1.9 difference, most people stay in one version, they don't switch very often.
I didn't say that this client would make people stop playing minecraft, it would just make less people play Cubecraft. For example, the badlion launcher you were talking about. I personally would stop playing on there if I had to switch to a different launcher each time I wanted to play a different server. Especially since so many servers have the same kind of games now.
Cubecraft is the server with more hackers currently, these measures are necessary