Bad map is hosted by players uncomfortable with faf, want to learn the game by making it as uninteractive as possible to learn the mechanics of eco ie “playing against yourself.”
These bad players progress into competitive players, however these “bad players” have now risen to 1000 rating or an equivalent. Like basically all competitive players with no reputation for competency, they rely on their rating for both proof of their ability as well as self assurance that they are any good/made any improvement.
So tell me why a 1000 rated astro or dual gap player will want to play a 1k+ 2v2. Hell, why would he want to play a wonder game. Not only does he get positive reinforcement to continue to play bad maps to continue the feedback cycle of gaining rating, but he will also get negative reinforcement by joining any other type of game and getting trashed both in game and in chat by everyone.
Then as his rating goes up, it gets harder and harder to transition between “good” and “bad“ games, and he might even build up a reputation as garbage at anything other than a single map which then can add another difficulty to shake off.