Earlier quoted context omitted.
Err, WhatsApp does use phone numbers as identifiers rather than service profiles, which is why it is ubiquitous in most of the world (much more than iMessage).
If you install WhatsApp and I don't, and you send a message to my number what happens? I know what happens with SMS and RCS (which falls back to SMS), which is that it works, because every phone has it. If WhatsApp doesn't just work, then it's at a severe disadvantage any way you look at it. Coordinating the 10 people in my family group to not only install a new app, but choose it the next time they want to send a me…
You can't, WhatsApp will only let you send to numbers that also have WhatsApp installed.
There's an "invite friends" sharesheet that will send a signup URL, but that's it.
> If WhatsApp doesn't just work, then it's at a severe disadvantage any way you look at it.
Ultimately WhatsApp has won in most of the world, so this clearly isn't that big of a problem.