Underbite
I think it's a matter of partying up.
If I squad up with just my one other friend, I'd like to do 2v2v2v2. And why not? It's not like we're taking up space in a 3v1v2v2 or a 4v2v2. Though I'm not opposed to a 2 stack playing a game of 4v4 either, just, maybe let us do duos when there are only two of us.
But if we're a 3 or 4 stack, then sure it makes sense to make us play 4v4. Besides, my friends and I would appreciate it, then we'd all be on the same team.