I think the holdup is that previously SMS was paid for through your carrier, so Google can let any app use it and no one loses money. Now the main RCS instance is hosted by Google, and I guess Google doesn’t want other apps freeloading on their servers since you’re not paying for RCS directly like you are paying your carrier. It really sucks and I hope it gets resolved soon, especially with Apple joining in. We also need a good open source RCS server and client.