For what it's worth, games like Dota 2 already default all communication on new accounts to "off". It's a rite of passage for new players to play some games and realize they haven't heard anyone say anything. Then they find the setting and realize they're being relentlessly flamed for being new.

Once you climb out of the beginner ranks, literally everyone has found the communication settings and has adjusted them to their preferences.

I agree that most of the time, people don't change defaults. But isn't true for team games in my experience.