"... younger consumers are concerned about being socially ostracized for not having an iPhone"
(Anyone remember the glory days of GAIM/Pidgin and multi-account messengers?)
Such things still exist, and even include iMessage ;-)
For Apple to open iMessage, would require that android manufacturers enroll the devices.
I use an iPhone, and I try to get all my friends to use signal
In addition, their continued reluctance to add an export or any kind of meaningful history backup is also a negative.
And it is not an issue anywhere else on Earth besides the US, people just use third-party messenger apps and that’s it.
That implies there was a time they weren't. They always have. If anything, in most cases the signals have been more diverse and therefore weaker over time.