SNL is not even close to 90 minutes. After subtracting the commercials, you’re left with barely over 60 minutes. From there, you’ve got to account for an INSANELY LONG intro credits, the “wacky photos of this week’s star” bumpers, the goodbye at the end, and the host’s monologue. Now you’re down to roughly 50 minutes.
From there, you’ve also got to deduct TWO musical performances to get to around 35 minutes. If you subtract the Weekend Update segment, you’re left with roughly 20–25 total minutes of sketch comedy in which to use all the cast members who aren’t a) the host, b) ringers like McCarthy and Baldwin, and c) aren’t doing political bits.
They usually only get 3–4 sketches per week that add up to about what you’d get on a scripted sitcom and yet they’ve got at least TWICE as many actors as a sitcom. Hard to include everybody with that formula even if they wanted to (and they obviously don’t).