So you depend on the company's goodwill. Has this ever worked when it comes to monopolized industries?

As others have mentioned, companies can (and some but not all do!) tie physical SIMs to a given IMEI just as well, so it‘s less a question of goodwill and more one of competition, consumer education and choice etc.

I think this (tieing phones to sims and vice versa) is forbidden in EU.

It's less about what's technically forbidden and more about what's actually enforced.

If the carrier forces you to spend an hour on hold to talk to a customer support agent to reissue an eSIM provisioning code, would that be considered tying? Probably not, yet it's still very effective at discouraging people from switching phones.