The iPhone transfer process actually tries to transfer the eSIM automatically, but it seems to require the carrier to support it.

I suspect Apple is still in the process of forcing every carrier to just support eSIM in the first place, before trying to push making it work well. The second part might end up being implemented through law though.

That's true.

I think carriers always need to be pushed via law. Australia mandated carriers to support number portability (including transfer time-frames) in 2001-ish. It suddenly became so easy to shop around, keeping your number was super easy.

Some started charging 'port out' fees, but that was squashed too.