Yamaha tried to renew interest in them a few years back, introducing some new models (the one with the P90's for a start). Unfortunately, they just didn't seem to catch on, or importantly, gain much promotional support. Yamaha released the RevStar around about the same time, and that seems to have gained far more promotion than the reissued SG's.
Whether it's a cost thing or what, I don't know. Most of the SG reissues were MIJ, and so were not cheap. In fact that they were priced against Gibson LP's and the "mid range" PRS guitars, as well as some smaller "boutique" manufacturers, which can't have helped, especially as the competitors were boasting figured timbers and other more cosmetic flourishes etc., etc. Rough deal? I think they kind of lost momentum in the early 90's, especially when the LP style guitar market was picking up again.