I do have a spare iPhone in a drawer, still works and can message on iMessage. There, I have purchased Apple hardware, now can I use iMessage on my Android phone?
For the same reason that if you buy a game for xbox, and then when you later buy a playstation you can't turn around and demand that MS port the various xbox services to the playstation, or a publisher port an xbox game to playstation.
For the same reason that if you buy a game for xbox, and then when you later buy a playstation you can't turn around and demand that MS port the various xbox services to the playstation, or a publisher port an xbox game to playstation.