At what point did society, unprompted and unquestioned, shift to using the Whatsapp phone app for actually important urgent serious things instead of, y'know, SMS or a phone call?
In some places the switch to these apps took longer (like France, because SMS had been free for a long time) but there is a fundamental asymmetry since SMS is free only for part of the users (so the others will never use it) while the apps are free for everyone. In the end, everyone ends up mostly using these apps.
Even I am guilty of that for both SMS and calls, having a single featureful app with contacts ordered by the most recent discussions descending (as in my country SMS is largely replaced by Whatsapp) leads to less friction than having to scroll through my actual phone's contact.
Almost all phone calls I receive are "actual" phone calls though. And SMS still gets plenty of use as the lowest common denominator for new recipients, but in practice over 95% of my received SMS are from computers now