Like jmondi mentioned, its' the default app for messaging on iPhones.

On top of that, switching to upgraded chats by switching platforms is not as easy as it sounds because you need to convince your friends to switch platforms. And that can be a hard ask, especially for friends and family that are less tech-savvy.

You could have people only message you via text, instead of iMessage, but doing that reliably is harder than switching platforms, unless you ask someone to disable iMessage in the messages app altogether, and no one wants to do that