>So when a friend of yours wants to message you and you don’t have the same app, what happens?

I tell the friend to call, text or email me. Price doesn't have any bearing because the market on messaging apps has bottomed out, in part due to Apple's app store policies.

I'm guessing you don't have friends spread out over several countries, where calling or texting is not a cheap (or even reliable) option.

And nobody checks email frequently enough.

But the point was a simple example. Clearly you seem to enjoy complexity more than me.