That keybinding works to go from insert to normal in most filetypes (looking at you sql) without the binding so unconfigured vims are still usable with it, and it's really easy to reach.

I will admit it's a little more awkward than caps-lock, but I use my caps-lock for ctrl and thus can caps-lock-c instead.

Escape isn't really useful anywhere else in the system, so capslock as ctrl or super makes more sense to me.