Probably because the pole they use won't fit in the photo studio.

Kidding. I really have no clue what they do with the pole. It would have to be a proper, working pole, fixed to the ceiling and floor so it can't move and fall over. Models might get *****.

I really don't know what they do with these pole thingies but when building stuff in the real world, they use what's known as an 'Acrow' bar. This is an adjustable set of tubes that uses a large, threaded mechanism that can extend the tube to support a heck of a lot of weight. It works like a car jack. Turning the 'nut' will extend the tube with tons of pressure.

I would want something like this mechanism if I was going to spin around a pole in this way. Ok. I might not look as pretty as the models we have here but back in my youth, I was a fearless gymnast that threw my body in the air in ways that what would scare my mother to death! How about running and diving off a trampet, 30 feet thru the air onto a crash mat? That was fun!