My wife's boss communicates with all her employees by SMS (mass SMS - works like group communication, both ways).
AddEdit: Airlines send their notifications and links to boarding passes etc. via SMS. Dentist and doctor appointments, other public office appointments (e.g. my upcoming passport renewal), document notifications (from pension fund insurance companies for example), public warnings ("Toxic fire nearby - close your windows"), and more, are via SMS where I live.
So if I'm not traveling I stay with the cheapest data option for my occasionally otg stuff and on heavy travel months I choose larger packages, because I found myself using more often, for example as access point to notebook.
I also have an Kaufland (Telekom) Prepaid card, that said it would provide basic, very slow internet, for free so that text messages over chat works, bur I don't know if I got the wrong APN settings, it has problems in my second slot or it only works if you top it up regularly, but that internet and rest never really worked, even the account management over the website doesn't really work for me.