Things would be a massive PITA without WhatsApp for me. I guess iMessage/RCS would do, or one of the many alternatives, but in the UK, WA is the messaging platform.
Honestly speaking I would not be in a leadership position for my Toastmasters groups if I needed to call each individual member every week as my other Toastmaster club does. That probably says something about me, but I'm sure many other folks would have a similar outlook.