The old notions of TV programming matter less and less as time goes on. If you own a DVR, a computer, and a DVD player, every night is a good TV night.
DVR's are great but they don't create desired programming where none exists.
And regarding Friday/Saturday evenings.....I remember even as a kid in the 50's it was a night mostly given over to the younger set. It would be easy for the networks to schedule feature films on these nights to attract whatever demo they are shooting for. Maybe that has become too costly, I'm not sure, but it was a big draw in the old days.