>being able to just show up in a country, download an app
This seems like a "draw the rest of the owl" situation. If I arrive in a new country with no phone data (which is why I need a sim in the first place) then how do I download an app? Being able to walk up to a guy at the airport and within seconds slide in a SIM solves that data problem.
not all airports have that. and even when they do I have had to fight to stay online or get online requiring entering email and clicking the link in the email before being granted online access.
As the other comment said it's either airport wifi, prep beforehand, roaming data (if absolutely necessary), or (last resort) you go to a physical phone store usually in an airport and they will set it up for you.
I can download T-Mobile eSIM from Australia - Pay them $15, know what my +1 USA number will be, all before leaving the country. You just can't do this with classical sims.
This seems like a "draw the rest of the owl" situation. If I arrive in a new country with no phone data (which is why I need a sim in the first place) then how do I download an app? Being able to walk up to a guy at the airport and within seconds slide in a SIM solves that data problem.