It’s because Apple has refused to adopt new messaging standards like RCS (not that Google is doing that much of a better job), but it’s purposefully broken interoperability to force people into buying into product ecosystems (iPhone vs. Android) to make you stick with one and get stuck on it.
It’s stupid anti-competitive and I freakin’ hate it.
Literally doesn’t have to be this way, it’s a choice (mostly by Apple, but once again doesn’t mean Google is better).
Apple was largely forced to support RCS in response to the mounting pressure from global regulators and competing companies. That may help explain the somewhat disgruntled approach to announcing its rollout in iOS 18.