If you are as old as me you remember Ma Bell invented JK. It used to be ~22ga 3 wire and it didn't really become 2 pair until the Princess phone (It's little, it's lovely and it lights) The yellow/black was the light, from the first wall wart.
Twisted pair started when multiple lines became an issue, usually in apartments.
Most single family phones still got wired with R/G/Y/B untwisted wire into the 80s. Computer modems and 2 line service brought the Cat 3 wire.
