well, btc could be used privately if the internet were not the biggest spy machine ever created. Although bitcoin doesn't have special mechanisms for privacy in the protocol, it doesn't have any mechanisms to identify users either. The privacy problems in bitcoin stem from the privacy problems on the interweb and the surveillance state.
Two BTC wallets, Samourai and Stashcrypto, implement the BIP47 protocol for Payment Channels. They offer payments and communications between Alice and Bob which cannot observe by Eve.