it already is, the entire protocol is reverse engineered, there are tools to automatically deobfuscate the code and there is already a full reimplementation of minecraft that also supports servers
Ever since I started playing it in the beta days I've been frustrated with how poorly Minecraft performs relative to what it's showing on the screen. (Not that that stopped me from pouring hundreds of hours into the damn thing.)
most servers leave it enabled because preventing player impersonation is pretty important so people can't just easily grief each other. some piracy servers implemented their own auth on top.