Are we talking strictly cam or adult in general?
Plenty of models hire professional photographers, I'm a photographer and I do photos for models quite a bit, both established and aspiring. The #1 reason a model would pay for a photographer is so they can have high-quality promotional or portfolio pictures that they have the rights to. A lot of models don't realize they are using photos they don't have commercial rights to, just because the photo is of you doesn't mean you own it.
Sometimes established models want photos with a specific look for their website, or they need full rights to a few pro-quality photos for promotional reasons (e.g: advertising at exhibition), or they just had a major look change and want to update their portfolio asap...there's lots of reasons a model would pay for a photographer.
But like Bianca said, it's not really necessary in cam/clip world. Self-shot pictures will suffice, especially if we're talking social media or amateur
content. Plus, we tend to get paid to pose, not the other way around. But ... like I said before, we don't always have the rights to those so we can't use them promotionally. Some of the big names in the "indie/amateur" world definitely hire photographers and camera operators for content and promo, but they make more a month than some Americans make in a year...soooo.
As a professional photographer and model, I'm a real stickler for high-quality images. I had some photos taken of me by a professional for my website, but it was a friendly exchange so I didn't pay them, they just gave me the rights to use them for whatever I want. I would have paid a friend, but otherwise, I wouldn't reach out to pay someone I didn't know and/or admire.
Now if you're asking this because you want to just start approaching cam models online and start offering to take photos for them, don't. We get that kind of shit daily and it's almost always a sure sign of someone with bad intentions. When a model needs photos they tend to reach out to someone whose work speaks for itself and they feel they can trust.