Given the sake of convenience & privacy advantages of RPCs, why don't more wallets implement this feature. From my understanding, Samurai Wallet is the only one who implements a RPC features (e.g PayNyms).
I have a long story about this one. But basically, the guy that wrote BIP0047 made some poor choices at the beginning. Some of those choices were called out by Luke Dash Jr and then the blocksize wars happened and the guy left for BCH. With no champion, the thing sort of just sat there.
If you're ever curious about it, ask and I'll tell you the whole story. It has a lot to do with some drama in the BTC community here in Austin from a while back.