For example, if you were coming to visit me in Australia, you could get an Optus eSim for the days you are here: https://www.optus.com.au/prepaid/esim
Annoyingly, its not yet perfect. Vodafone for example can do prepaid, but requires the prepaid physical SIM to be activated first then transferred: a Vodafone store can do it of course, but that's a pain.
https://www.vodafone.com.au/support/device/esim?accordion-id...
I imagine this will get better as time goes on, though.
Woolworths can do pure online eSim only prepaid: https://mobile.woolworths.com.au/mobile-phone/esim
I’ve spent time in both the UK and Mexico this year and it would have cost 2-5x as much if I couldn’t get use a physical SIM.
But again I love the app and hope something like that becomes big enough that the big operators will integrate with it.