It's so you can make a 3x3 block with short buses
/invade /invade /invade
/invade /invade /invade
/invade /invade /invade
Lol nah, on a serious note, it is still there because why use / invade if invades are pretty much already welcome. It is not needed and got really annoying. If a thread does not welcome invades, then you don't invade it, simple as that, but don't need / invade for any reason at all.