If you are all about the self promotion its hard to be part of a culture of discipline. Having a rule of what happens in the gym stays in the gym allows people to be more free then they can when possibly being filmed in private moments.
Just the other day I was at the gym and this very large dude was walking to a machine with what I thought was a cane/crutch. Then I realized it was a tripod style selfie stick for shooting his workout. There are actually quite a few "Influencer" wanna-bees at my gym. I find it so weird when two girls are filing themselves working out. It can affect the atmosphere for sure. But that is the culture of this gym and I don't try to change it. I have to work within that culture. In fact my gym is the home gym of the current "Worlds Strongest Man". Other gyms I have been at there are no cameras allowed.