Because iMessage is the only way to send SMS on an iPhone I think they should be treated as a gatekeeper. It's not like there is another SMS app and iMessage it's a secondary app. Apple is trying to say they are like Whatsapp and others, but they're not. Whatsapp isn't tied to SMS.
So if they are going to continue to control SMS access, they need to support RCS.
Plus, I can't get any family iPhone users to install an alternate messaging app. They're not going to install it just for me. Some have FB Messenger.
I've had arguments about the fact that because I'm in their group it lowers videos and pictures quality that gets sent to the group.