I just had that conversation with a group of adults who all had iPhones and were unwilling to add non-iPhone people to a group or change messaging apps.

The reasons given were:

• My iPhone is too old, I can't install another messaging app.
• I'm not going to install another app where I have to remember another password.
• Messages don't go through when we add a non-iPhone user to the group.

The conclusion by the group was "just buy an iPhone!"

And that's a group of adults. I can't imagine the bullying and peer pressure teenagers have to face over something as idiotic as messaging apps.