It’s not just config though (unless you consider logic to be config). When you’re roaming, the sim applet has to generate a path back to its home network based on request/responses with the networks it can see and their partners (and their partners’ partners etc.)
It’s effectively multi-hop peer discovery and I don’t think you can encode the general case logic for it as just config.
Edit: as a (rather niche) example, FirstNet sims run a different applet to AT&T sims despite nominal running on the same network because they have special logic to use more networks if they are in an emergency area.
So for people who don't plan to roam, what's the point of a SIM card (embedded or not)? Credentials and a few lines of config should be enough. Do the carriers benefit when users use a SIM card?
It’s effectively multi-hop peer discovery and I don’t think you can encode the general case logic for it as just config.
Edit: as a (rather niche) example, FirstNet sims run a different applet to AT&T sims despite nominal running on the same network because they have special logic to use more networks if they are in an emergency area.