Camera makers love this idea. Other people do the software engineering for free, and they profit from it. Kinda a win-win.
As far as a mirror lock up button, on the newer Canon DSLRs I think you can set the mirror lock up and then save that as a custom setting, or better yet, as a file with the mirror lock up in it. then you just "load" the file back and the mirror is locked up. that way you don't need to dig for the ML setting in the menu. Not as good as a button, but closer.