I only use the Messages app to get MFA codes for different applications. Don't they use something like Whatsapp in the US? I think it mostly a non-issue in Europe
Clearly there are network effects, and which app wins is varies between regions and groups.
The only difference I can see is the lack of end-to-end encryption and reactions (e.g. like a message)?
This is the reason I haven't switched to Android—so it has worked on me at least.
I'm sure it does depend on your community too, e.g. iPhones are more common among members of the upper-middle class. (Which is why iPhone use is well above 60% in my social circle.)