[dboreham]

Quick note that I'm in the US and my experience is: most random people use SMS; closer friends and family some use Signal, some Discord, some email; colleagues use Slack; overseas taxi drivers etc. use WhatsApp.

[pkamb]

By "use SMS" you surely mean "use iMessage" much of the time.

[spunker540]

If op is on android they wont know who uses imessage