I remember when everyone was freaking out that there was no teaparty maps. Now there's a lot of this map type. Either way, I do agree that teaparty has been the most shown map on the board.
This could be since teaparty could hold up to 40 players, it might take a while for the game to start, hence why the signs are still there waiting for people to join. (This is a theory, so don't quote me on this.)