alt Hacker Newshow do imessage and android users communicate with each others? Do android users really still use sms to reach apple users? Don't they have group chats everywhere?
Here in europe every club/association/group has a whatsapp group chat. For instance here since the official app provided by the government has a super clunky UX most people get information from primary school through a whatsapp group chat managed by the parent's representative who has exclusive access to teaching group.
Yes, I text my brother who has an iphone. Thats our primary communication when not speaking.
As a counter to your question I've never used whatsapp and never saw a reason. What group chats? Are they groups of personal friends or mostly things you would 'follow' like a football club?