It’s just the network effect. Here unfortunately it’s WhatsApp, you pretty much have to use it because people organize events in groups with it and whatnot, and you’re the weirdo if you don’t have it. I actually deleted my account for a couple years but recently caved and made one again because people just wouldn’t use anything else and having someone else relay messages is annoying for both them and me.
I use iMessage when it’s available but I wish for groups (or just in general tbh) everyone would just use Signal because it’s both not tied to an expensive device and also not owned by a corporation with a track record of shamelessly exploiting user data.