This is completely personal preference and I would never enforce it, but I hate when people dial in to a video conference or other meeting. Even when the camera is off, having 10 people on a call but 15 attendees that include a bunch of random phone numbers, combined with not having any idea who is speaking if you don't know everyone's voice by heart, makes it a very suboptimal experience.
If everyone had a nice camera, nice microphone, and nice headphones (I think all three of these should be provided by employers to remote workers), and just used the video conferencing software the way it was designed, a lot of the friction and annoyances would go away.