Teams would be stupid in a lot of formats. For example this one.
Glacial Chasm +
Jinxed Choker +
Mishra's WorkshopHunted Phantasm +
Black Lotus +
Wastelanda 3rd deck I haven't shared yet that counters their bad matchups while still doing well enough
^^ A team of 3 could release these three things and have a decently high score.
Only if they judge the format correctly. If as a team you hedge, you're likely to hit a middle-ground that doesn't have the possibility for quality wins. Team formats with collective scores naturally push scores toward the middle, which makes meta-gaming that much more important. Also, a team format gives you a natural way to talk about formats with another person without your research getting used by the public at large.
Basically, it would remove a ton of the risk from the game because you could release multiple really really good things and do semi-well to average vs most metas. This would be unfair to single players who wouldn't have a hedge against their one deck just stupidly bombing (like a few first round decks we can use as obvious examples).
There's not a ton of risk in the game as is. People tend to (a) run something familiar, (b) run something clever, or (c) run something that's winning their perceived meta-game. There isn't a lot of leveraging beyond that. Yes, the scores will tend to average out more, but again, this format puts a higher premium on being able to properly find the good decks and meta-game accordingly. There wouldn't be single-players; everyone would be part of a team.
@POSV: Two players is probably much better, if for no other reason than making communication easier. It could also be run as a single tournament where everyone gets to play with every other person at least once.