It kind of makes sense though. The dominant messaging app has always varied by region. The US is just really unlucky that the one that won there happens to be owned by Apple. And I say "unlucky" - it's not really luck. iMessage could only ever dominate in the US really because iPhones are very popular there and because SMS is free.

In most of the world iPhones aren't nearly as dominant so nobody would use iMessage or they wouldn't be able to talk to half their friends, and there was a much bigger incentive to just ditch SMS-related systems entirely.