All while I receive whatsapp/telegram message spam on a fairly regular basis, despite not being active in any groups or channels on those apps (and in general, opening them maybe once or twice a week at most). The only reason I even use those 2 apps is to talk to select few old relatives of mine who are not very tech literate and who just happened to learn how to use those apps +a couple of friends who simply insist on using those apps.
1. It's multi-device at least when we're talking about non-phones; that's one of its better features, being able to use it from your Mac or iPad
2. You can make an iMessage account without having an iPhone; just having an email/Apple ID and some other Apple device to use it from
3. If you had an Android phone, presumably you wouldn't also have an iPhone at the same time? And even if you were using it on an iPhone, it seems like nothing stops you from being logged in on a second iPhone