Another anecdotal UK experience: all contact with humans is via WhatsApp except one older relative. My SMS inbox is 99% 2FA codes, appointment reminders and delivery updates
Sms is mostly for when you want to add urgency and be less likely to be muted.
I would love to get rid of WhatsApp due to FB and hope to do so somehow soon.
(except that there's no exception; it's all whatsapp)