True. But what they are doing now is a clear loser.
It is not only about getting people to iOS though, as I have written. Apple Music and Apple Pay (and other services) on Android can also generate income without people switching.
Even more importantly, creating THE major app used by everyone throughout the day, even by people on other platforms, is so much more worth than everything else Apple does to promote whatever other services Apple will come up with in the next years/decade. As it stands now, nobody not invested in Apple's ecosystem even considers Apple's services like Apple Music or Apple TV+ over its competitors, because: Apple. Making a piece of software the whole world uses for their everyday tasks would have changed people's view of Apple as a walled-off player.
The whole thing is a major strategic blunder. Not only is it a missed chance, iMessage will also simply cease to exist once it has become redundant in the US too. People may not really understand the issue because they are using iMessage every day, but just consider this: My family uses Macs, my workplace uses Macs, many of my friends are on iOS, yet nobody I know EVER uses iMessage. It's not used only 50% of the time or so. It's not used at all (Europe).