I have almost never needed video but certainly a voice conversation is much, much faster for two or three people to work something out.

Four+ people and someone is either being held hostage to others and/or just tuning out. The more participants, the more of this that’s happening. And that translates pretty directly to lost time, money, and focus.

I don’t think Teams supports it, but it would be interesting to see studies where orgs go “max participants = 4” without high level approval.

I think it depends on the person. For me, for example, text work best for any kind of question, no matter how complex. On the other hand, for simple questions, when I just want to chat, I'll opt for a call or meet in person.