Obviously it's not the reality that these are easily available in all destinations, yet, but should become more so over time.
Besides, I doubt roaming fees are all that lucrative considering all the "free global roaming" plans there are now days. Those networks that charge crazy per-MB roaming rates are, presumably, keeping most of it for themselves.
The last several times I've bought SIMs outside Europe, I've had to show my passport.
Are you sure it's EU law? I can't find anything on it.
Anyway, besides Britain (both before and after Brexit), there is only a handful of countries in EU that do not require ID, among them Denmark:
https://www.comparitech.com/blog/vpn-privacy/sim-card-regist...
most do require it.
I think you are getting scammed: airport SIMs are way more expensive than actual SIMs you get in town and eSIM you get on an app like Airalo. International providers are obsolete in the age of the eSIM, since you can get a local provider at the click of a button.
eSIMs are still a bit more expensive than physical SIMs you buy in a phone shop far from any airport... but that expense is worth having internet from the second you land.
My only disappointment with this is how hard it is to migrate, but eSIMs work perfectly for travelling.
That's definitely not true for many of the places I've visited. Additionally, the airport SIM shops are often the only retailers that know how to register/KYC SIM cards with international passports and/or where the staff speaks English.
For many years I've owned dual-SIM phones and on many occasions have bought a local SIM a the airport or corner store when travelling for a week or more to countires outside my roaming allowance. This is almost always cheap, usually also easy, but can sometimes be a hassle if it takes a bit of time to track down the SIM.
When I bought my current phone with one physical and one eSIM, I was expecting it to be a huge improvement. The reality so far has been rather different... Twice now I have had to waste a lot of time online shopping around to find an eSIM for the destination country. Most of the international providers are surprisingly expensive (often 10x the cost of a locally bought SIM), have awful websites that look like they were thrown together in a weekend, and they often require you to install their own app to manage the eSIM/account, which is also invariably awful. You're also less likely to have much choice of which network you end up on, which can be a significant issue in less developed countries.
Now that I only have one physical SIM slot and always need it for my home country SIM (my mobile provider doesn't yet even support eSIMs) I regret chosing eSIM over a dual SIM phone. I do expect the situation to improve, but for now at least it still feels like a big step backwards for travel compared to dual SIM.