Comment by Cthulhu_

Part of that is because of the trend from the past few years (ever since Lost I believe but there's probably previous like soap operas) that TV shows are continuous. But even the 90's TV shows would have some continuity, referencing previous events. That said, I've been rewatching Star Trek DS9 (and may do so with Stargate as well) and the main overarching plot beats often happen at the start and end of a season, the episodes in between can often be randomised.