Most US carriers have rolled it out by now (or can be completely circumvented by using Android Messages app) and the green bubble teasing seems like a USA specific phenomena.

Anyhow, so what you mean to say, is that it's not about security (because it's present and accessible), but it's about appearances. And worst, the platform perpetuating the the appearances is not making any moves to secure it's messaging to non-Apple devices. Unacceptable.