How do you know $worker isn't performing $job because they were forced to? If you're going to make the pearl-clutching argument that /anyone/ can potentially be in a coercive situation, then apply to to genuinely anyone, not just sex workers.
I don't think the risks of porn and other online content are comparable at all. If I'm watching your average YouTube video, I don't doubt for a second that the content on display was made intentionally by the video host. Your angry ex won't upload your comprehensive four hour Minecraft tutorial or the video detailing how you constructed your own army of garden gnomes.
Coercion might be a risk present in any media but there are definitely areas where the risk and impact are much higher than in others.
Why not? Parents pressuring children to gain celebrity status isn't exactly an undocumented phenomenon.