I'm surprised there aren't more full tapings of 90's television available, as in entire blocks of broadcasting with all the commercials intact. That was how most recording would have happened, and with the start of TV Land the networks should have been able to predict there'd be a market for it in 30 years.
Storage was a problem back then.
Not really. Hoarders were already mass recording TV from home, see
https://en.wikipedia.org/wiki/Marion_StokesRecording ~5 hours of television a night would have been a trivial cost for a network like NBC. Particularly compared to the licensing fees those hours would have had.
Really. Tape media is bulky, expensive, prone to deterioration and the content back then started off low quality, so that deterioration takes a meaningful toll. Sure, a major corporation could afford to archive and maintain all of that material, but what's in it for them? A few thousand hours of repeating commercials and station promos?