TL;DR
- Users who have rooted their phone, have their bootloader unlocked or are using some custom ROMs report that their RCS messages are not being sent, even though RCS shows them as connected.
- The Google Messages app does not show any error messages when blocking RCS messages of these users and does not send the messages out as SMS or MMS either.
- Google famously campaigned for Apple to include RCS messaging in iMessage but is now blocking it for certain Android users.
Probably for “security reasons”
No, they want people part of their ecosystem (play services) so they can spy on you better. And incase ya forgot RCS could be a potential attack vector as it is more code that can possibly be used for nefarious actors.
MMS can be easily be used this way because of auto retrieval of pictures that have been modified with code that auto runs once downloaded and opened by the messaging app.
On older Android devices vulnerable to Stagefright, malicious code will auto-run as soon as the MMS picture preview is loaded by the system notification shade, if I’m not mistaken