interestingasfuck

Sure, but that's not how it tends to work. That's why there are all these stories about singers being mistreated by their record labels. The record labels could just license the works from the artist. But, that gives the artist some control. Record labels much prefer a situation where they're fully in control, and own everything the artist produces. It's typically only the top 0.1% of music acts that are so powerful that they're able to take control over their own output and license it instead of simply assigning the copyright.

I'm sure it would be the same for modelling if there was a copyright to someone's body. The modelling agency wouldn't want to risk that the model could go to a rival agency. A standard modelling contract would then involve assigning the rights to the model's body copyright to the modelling agency, and only the most powerful and in-demand models could possibly resist that and keep their rights and only license their images.