Yes, I understand that.

> not as in “big government tell everyone what to do”, but as in “let the market do its job properly”

You are missing a crucial point: the current state of Big Social Media is a product of a free market. Users freely choose to take advantage of the opportunity to use these services without paying for them. "Making it illegal" would mean telling all those users that they can no longer make that choice because the government is taking it away, by passing laws that prevent Big Social Media from offering their services for free. And of course Big Social Media will play that for all it's worth in the political debate that would precede the hypothetical passage of any such law. Not to mention that such a law would also be outlawing all the other tech startups that would benefit from a "freemium" business model.

My prediction is that any such law would be taken off the table due to political pressure long before it got anywhere near actually being passed. But in any case, saying that the law is just to "let the market do its job properly" is obviously wrong. "Free market" doesn't mean you get to outlaw freely chosen transactions that you don't like.

> If it’s illegal, they would have no other choice would they!

If we assume the law you propose actually works and isn't gamed (which is already a big if), my prediction is that Big Social Media would either pivot to some new thing that they could charge for (LLM-based "AI", perhaps), or take their cash and effectively go out of business. I don't think they would just say "oh, well" and actually do the hard work it would take to make all their users paying customers.