Sure, but they wont. The insidious thing about iMessenger is that it isnt iChat. It is the apple default text messaging app. Which is good because it means that all your messages are in one place, and you dont have to try to convince your older family member to install a 3rd party chat app. You just have a chat app. This tricks users not into thinking that texting is just better on apple.
But its bad because it only works between other apple products and users. This is objectively Apple’s shortcoming, however there are enough iPhones in the wild and enough people in the US who defaulted to just hitting the sms/mms icon instead of downloading a chat app that the odd man out might be the android user. And it’s not just about the green bubble being green. If you invite an a green bubble to a group text then all your rich chat messenger features go away and it turns into an MMS thread. Which is objectively bad.
But yes they could just download and use whatsapp,line, telegram, signal, facebook messenger(and in the early days things like aim/yim/msn) But they dont. The fact is their default messenger app works, and it works well with most people they talk to so the problem is the green text.
It’s especially silly when you consider the “there’s an app for that” generation of user and so many things are apps but they refuse to engage on other chat channels. People download different apps to get dates, the navigate, to browse websites that shouldnt even be apps, to order food, order groceries, order taxi’s, but a chat app just to talk with you? ehhhhhhhhh.