Seems like it would be a great way to expand the usability of Bitcoin, i.e. tell your friends to send their transactions to your node when they are not at home and then their client software only needs to manage simple wallet / key operations. Curious why this is not common practice.
The Bitcoin Core RPC interface is a private interface not suitable to be exposed publicly or accessed by untrusted parties.
On the other hand it is quite popular for people to host public or semi-public Electrum servers. This way stranger or friends can point their wallet to this server to fetch information about their coins from the Bitcoin network.