If you think about, how this simplifies anything, you will start to understand the mess that is the FF codebase (not that chrome is noticeably better, particularly if you try and build it anywhere outside of ubuntu/x86_64).
It's not a mess, it's just a case of "not used by me, so remove it". Instead of improving the feature they let it rot away, like so many others, and then ignore that people still used it. Really sad.
My thought too! Legacy extension APIs are one thing. An extra DB column / key:value pair is nothing.