Where I live, many ISPs tie public IPs to static IPs if they are using CG-NAT. But of course there are other options as well. My point was that the other options don’t disappear.
Though I do get the point that Cloudflare aren’t giving away something for nothing. The main reason to me is to get hobbiest using it so they start using it (on paid plans) in their work, or otherwise get people to upgrade to paid plans. However, the “give something away for free until they can’t live without it then force them to pay” model is pretty classic in tech by now.