Do you think that international travelers don't have mobile phones? Really? Same for expats - most immigrants I meet have mobile phones. (I am an immigrant, and meet a fair amount of other immigrants, from various backgrounds, various income levels, and various sorts of jobs). I had to look up to see if the country I'm in even offered residential landline service, honestly.

Not everyone has a smartphone, but that's not what is required. Just a mobile phone that can receive an SMS - and phones have been doing that for 25 years or something.