They aren't conscripts so its immaterial. The only thing that matters, IMO, is that to which they did not sign over their rights which is their likeness.
As for amateur athletics, I think both sides know what they're getting into when they do that. Its an apprenticeship of sorts. For that they get excellent trainers, lots of food, opportunities to travel, BMOC status, and often discounted or free education. When you are an amateur YOU VOLUNTEER. YOU made that decision. You aren't owed a right as such. Did you know that graduate school work, which could be highly valuable to a university, is not yours. It belongs to the university. A professor develops a patent and immediately transfers it to the school. In all these cases the people were free to choose given the choices in front of them.
Now, one could argue that the market is held tight and is some form of anti-trust collusion. But that's an entirely different argument which has little to do with the appropriation of a person's image.