Sure, there are many underpaid studio girls on cam sites, but, in my opinion, they're better off in a studio.
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Tube sites have a ton of free videos, but most of them are of crappy quality.
I don't mind paying for porn, but then I'm stuck with mainly the same type of hardcore content and the same pornstars appearing in scene after scene where I have no control over the action.
Cam sites have tens of thousands of performers, like Rabbits Cams for instance, with dozens of new ones appearing every day offering much appreciated variety and freshness.
Although, many guys fall for one particular model and that may leave them wanting more when she disappears. I often find myself really enjoying a certain angle and/or position in a porn movie only to have the camera angle change and the performers switch positions.