A lot of it is driven by differing low end data plans. In some countries even the cheapest tariff has adequate data allowance, in other countries, data is an ex

A lot of it is driven by differing low end data plans. In some countries even the cheapest tariff has adequate data allowance, in other countries, data is an expensive add-on. So it's entirely conceivable that in some places, someone with a limited income only has SMS bundled as a free service on their plan, with data either not enabled, or expensive pay-as-you-go. Therefore in that demographic SMS messaging will be the primary method. In the UK, almost all tariffs come with a bundle of data, so SMS has all but died out (except for automated parcel delivery updates, and 2FA authentication et al.).