While teams is super inefficient, 10 years ago no one was casually streaming 4k with a webcam feed in a remote team session with 2-10 people.
aren't most webcams on laptops firmly in the 720p-1080p territory? I know most people receive 480p streams.
I'll grant you that 10 way calls were much less common then, but even now Teams only shows 4(?) of them depending on UI layout.
My teams shows up to 8 I think.