I actually agree here. The issue would be third party iMessage apps and other things iMessages can do that are heavily integrated within the Apple platform like sending Apple Cash to others through it, Animoji and Memoji, sticker packs, etc..
IMHO they shouldn’t even attempt to support those features but they could certainly bring the base functionality of iMessages to Android. Look at what they’ve done with Apple Music and Apple TV. Talk about apps and services that are available on multiple platforms and devices. Particularly the Apple TV app.
The difference being service revenue. Apple Music and Apple TV are apps that deliver Apple services and generate revenue. What money is there really to be made by porting iMessages to Android and/or Windows? There isn’t unless they charge non-iPhone users and I doubt that would fly. Perhaps a bundle? For $0.99 more a month you can get iMessages if you are subscribed to either Apple Music or Apple TV+ on another platform and if you subscribe to both it’s included for free?
The exposure would increase their user base but by a factor of what and how do you monetize it without charging a fee that nobody will pay or trading end user privacy for advertising dollars which is a game Apple has built a business model
and reputation around avoiding?
It might get some people to look into switching to an iPhone but I just think the market is so mature now that most users are either iPhone users or Android users and the chances of getting them to switch are slim to none. Once established most people stick to what they know. Maybe in the early days when iMessages first became a thing and was way ahead of SMS messages but that ship sailed a long time ago.