Android phones are free? I have to buy the phone no matter what, so I don't see that as a differentiator.
I don't want multiple ecosystems that don't interoperate at all. I don't want to give my private conversations over to an ad company like Facebook. I like iMessage because it adds features without taking. I don't worry about what app I need to use depending on who I want to talk to, I just send them a message and move on with my life.
I know what argument you're trying to make, but I think it is disingenuous to pretend that WhatsApp is free while iMessage is not. As a practical matter neither is free, and both are free.
I don't want multiple ecosystems that don't interoperate at all. I don't want to give my private conversations over to an ad company like Facebook. I like iMessage because it adds features without taking. I don't worry about what app I need to use depending on who I want to talk to, I just send them a message and move on with my life.