I don't know that it's necessarily that, simply that SMS became very heavily used _and still is_ for basic functionality, essential services, billing, notificat

I don't know that it's necessarily that, simply that SMS became very heavily used _and still is_ for basic functionality, essential services, billing, notifications etc. in Europe, Africa, Asia - unlike the US. Compare to e.g. the US requirement for universal lifeline (landline) phone service.