An excellent article raising some important points. Here are my thoughts:

1) Personality and temperament are huge factors, as you correctly point out. As a fairly stereotypical INTJ (to use the Myers Briggs personality test), I'm a rather extreme introvert, so no, I don't want my camera on in meetings.

2) A "camera on" culture doesn't allow for things like autism spectrum issues. I believe I am probably on the spectrum and have gone undiagnosed for decades (though, after years of my wife urging me to get tested, I am now in the process of doing so). I will tell you this much: For me, video conferencing is fine in Star Trek, but in real life, I don't like it one bit. Television shouldn't look at you. It just feels wrong, and if I don't keep my camera off, I can't concentrate properly on what is being said.

3) Meetings are often a monumental waste of time, and there are countless interminable interactions of this kind I have endured that all too often could have been resolved in a simple email, or involve keeping loads of people present to listen to a surging tide of irrelevancy that has nothing to do with them. In such circumstances, yes, absolutely check emails, phone messages, get a snack, or carry on with other tasks. If the company you work for are foolish enough to insist you sit through such tedium, productivity is better than daydreaming.

4) I have always insisted on having my camera off for work meetings for this simple reason: If I wouldn't invite you into my home, I see no reason for you to be allowed access to it via video surveillance. If it is really that important to see my face (which it isn't), I'll come into the office and speak to colleagues in person.

5) As long as the work is being done, and done well, who gives an airborne fornication if someone keeps their camera off? Controlling, paranoid, petty, micro-managing, bureaucrat bosses. If you have one of those, I recommend finding a different job.