Steve Jobs famously believed in cannibalizing their own sales. (Or, to be less charitably, he believed in that when it was convenient to believe that).
Whether the culture has carried over, who knows.
Even as an iPhone user, I never would have thought iMessage was even in the top 5 or 10 reasons to keep using the platform. But I'm old, don't text all that much, and have unlimited SMS anyway.
I imagine all the cool kids these days are using alternative data-based services anyway. Snapchat, the like. For us old folks, WhatsApp, GroupMe, etc.
It's not necessarily the experience on the phone that is lacking in other SMS based apps on competing platforms -- I see it as the ability to leverage being able to message anyone from most platforms be it conputer, iPad, or phone and have it all in sync. That to me is the massive draw to it.
I kind of wonder if there isn't more to this. Perhaps it's why Continuity [1] never fulfilled its full vision of moving seamlessly between iOS and macOS. Lack of support for third party apps, especially messaging apps, felt intentional.
