I‘m staying in a remote Italian region, mobile internet is almost nonexistent because antennas overbooking or something similar.
I bought a data-only eSIM from Airalo, that is able to connect to 3 (!!) different carriers, one of which works extremely well around here. It’s not cheap - 16€/10GB - but the convenience is top notch. There are many data-only eSIM global providers out there, you just have to search for them with the right keywords. I believe those services are mainly aimed at digital nomads.
My experience with eSIM has been with my Apple phone. I have an app that basically does this - it's Ubigi and I've generally been happy with it. I installed it from the App Store.
As to why Apple themselves don't have such an app, I would have to assume that it's because they don't see reselling of mobile data as a core competency nor a profitable business line.
I just have a provider (Google Fi) that works worldwide. I have no desire to negotiate a deal with anyone. Each spend point is a pain point. Prefer a single aggregate plan. I put my money in and I go anywhere in the world with my phone. Works great. Been fine for me for over five years.
