A few videos had them, like Horizon on the Middle of Nowhere s2 Op (Zone//Alone) had the lyrics and stuff. I think I read somewhere they have to go through the same licensing process for the musics and translations...
Licensing isn't exactly the right word - rather than licensing, it's that the lyric translations have to be approved for the songs, which may will end up having to go all the way back to the original artists. It can be an incredibly tricky and time-consuming process to go through, and when you're trying to get a show out on a tight schedule, probably a little too much to ask.
What is weird, though, is that AKB0048 and Love Live have all their insert songs subtitled, but not their OP/EDs.