That's because the default is 99% the way the app is designed to be used. If the default is regulated, then they will just say "sorry the default is boring, click here to bring back the feed" and everyone will just click.

As a matter of fact, the social media companies will then have an incentive to make the default really bad, which is absolutely what they will do. This would be the malicious compliance I was referring to elsewhere.

I think most people over here are oversimplifying this and underestimating the ability of these companies to get what they want.