This is fixed in iOS 12.3 [1] and macOS 10.14.5 [2], both released on May 13th. As Natalie noted on the ticket, turning off iMessage will also prevent the bug.
Also if I switch to Android I don’t have to worry about disabling iMessage before. (Not that anybody in my country would ever send an iMessage or an SMS though...)
Not sure what pop-up you're talking about then.
This shows up when you insert a sim that’s not activated with iMessage. Maybe it depends on your region. In my country you really have to pay because the activation process sends an sms message.
All those features in a market where lots of people you'd be chatting with are on Android, I'd suspect.
There was also a bug that allowed a malicious message to crash phones sometime last year where the recommended fix was turning off iMessage (similar to this one).
Some folks probably don't remember to turn it back on after these incidents.
While there are a lot of reasons not to want to use iMessage but only being able to talk to other iOS users isn’t one.
iMessage is a subset of features in the Messages app that are unavailable when communicating with someone on a non-Apple device or if one of the parties has iMessage turned off.
iMessage is not that app unless 100% of the people you message use iPhones.
Ugh, so sick of seeing that