In my experience, incoming SMS are mostly spam, and other low trust notifications, while incoming iMessages, even if unknown to me, are likely to be real people. Buying an Apple device is an expensive signal, and Apple will quickly shut down abusers, maintaining that relatively high bar.

Letting (actual) Android users use iMessage probably wouldn’t affect that, but the open source hack/reversing of it opened the door to iMessage spam that Apple, for the sake of reputation, and customer satisfaction, is obliged to close.

Anyway, I guess my point is that there are some “burdens” that are less obvious than others.