There are performance features that are impractical to deploy unencrypted, so browsers only enable them on HTTPS. (Notably: HTTP/2 and Brotli.) There are plent

There are performance features that are impractical to deploy unencrypted, so browsers only enable them on HTTPS. (Notably: HTTP/2 and Brotli.) There are plenty of middlebox devices on the Internet that will drop your traffic if you send anything HTTP over them that they don't understand. So you're kinda "locked in" in not deploying new protocol features. Encryption provides a way out of this.