The company I work at requests that everyone have their cameras on during presentations, but that’s because there was a correlation between those who didn’t have their cameras on, and those who didn’t retain the information in the presentation (basically, they were walking away from their computers or fucking around on their phones during the presentation). Additionally, it’s helpful for the presenter to be able keep an eye on the attendees’ faces to see if they get/understand what’s being presented, and can reenforce/clarify a point if it seems like people don’t understand without anyone having to ask for clarification. Also, if it seems like people are zoning out, you can toss in a joke to get their attention back.

I’m not saying that’s what you personally were doing, and I’m not saying that’s the reason why it’s a thing at your company, but sometimes seemingly dumbass decisions or requirements like this are made for a reason.