Businesses chose Teams not because of anything listed in this thread of comments. Businesses also didn't choose IE because it's fast and had a lot of features.
People chose Skype because it was fast and it just worked. It stopped being fast and people moved over.
Where's the fifteen year old IRC client which does hardware accelerated video chat from a web browser?
> "In fact, today we don't need a document editor embedded in a chat app."
What can be asserted without evidence can be dismissed without evidence. Except we have evidence: given a choice of Teams or IRC, businesses choose Teams.