To be honest I don't know anyone in Europe using iMessages. We are using Viber, WhatsApp, Messenger, Signal, Telegram, Threema, etc. and none of those options are iOS or Android exclusive.
iMessage is a typical American thing which, we Europeans, have a really hard time comprehending what is the obsession with it.
And we also have a much bigger Android market share, so it would be stupid for iOS users to use some messaging app, that would be iOS exclusive.