Consider whether Apple has changed their position about shipping key functionalities of their platform to non-Apple devices in the decade since then, in light of (for example) their purchase of and continued offerings of Android-friendly Beats products, their beta of Apple Music as a webpage in any browser, and their TV services app spreading to every smart television platform that competes with Apple TVs.

Those other products have their own revenue streams. Apple would not profit from allowing access to iMessage without owning an Apple device.

You can't even get their browser on another platform.