I was not qualified to contribute to Russian, for example, it's not like you just ask and you get to help, you audition. There just may not be anyone offering to build a course, or anyone they feel can.
Nobody is stopping anyone else from offering those others. I'm sure people are working to figure out how to incorporate those languages into Duo, given how many people bitch about those languages. Those other languages would be harder given the current system.
Cyrillic is easy to teach, just a few extra lessons. The reason Duo hasn't offered most of those is because it's only about to launch its first non Latin alphabet based language soon.
