I must admit I’m one of those always-on people and everyone in our team does so. For those speaking I feel it is quite rude to not give them any visual cue on how they are doing: I’m I understood? Are my points appreciated? Do I bore people? Are people even listening?

Personally, I think the only good reasons to turn off a camera are either technical issues or if you indeed briefly want to send the message “I am distracted for a short while, but will be back with full focus in a while”

To your other points:

- Don’t like your own image: turn self-view off

- Messy background: enable blurring (or an alternative background)