Sugar Motta and Joe Hart’s departure from the show

What’s your head-canon as to why these two were unceremoniously written out of the show? Like, TPTB couldn’t even give us a small hand wave or throwaway line explaining their absence. A simple “Joe and Sugar have other commitments and won’t be joining us in Nationals…” by Mr. Schuester would’ve sufficed. I guess we’re to assume whatever happened to them was explained or transpired offscreen. They were very much apart of the show choir and it was never explained to the audience what happened to them. Perhaps, if we look at the nonexistent subtext, it can be interpreted as a commentary on how people come-and-go but life goes on(?)…however, maybe the exposition given in 6x10 by Joe Hart on how Sue cut his (culturally insensitive) dreadlocks was the reason he quit glee club and Sugar followed him…just because