Automatic keyboard sharing is just a small step away from that, but that seems
really annoying to me. I'd rather control when I want to share.
Why not just have a proper shared clipboard plus keyboard/mouse sharing in a multi-computer, multi-monitor setup?
Because if you don't need keyboard/mouse sharing that's just bloat running on your machine, because you become dependent on yet another utility that may be discontinued or receive a crappy update at any time, because it's less flexible (can I share only on demand?), less portable and it costs $50 that would be better spent on blackjack and hookers (or whatever you do for relaxing).