W1zardK1ng Beeper RCS requires you to have Google Messages on your phone. I believe they are just using messages web portal to sync messages between the app and google messages as it does not act as a fully fledged sms/rcs client. It's the same with WA and telegram, you essentially need to keep the apps on your phone for them to work (I suppose you could delete the app, but there would be no way for you to recover anything if something goes wrong). Beeper is useful (for me) for insta chat though as it allows me to not have the instagram app on my phone