The difference is that VHS sales gave way to DVD sales at comparable prices, vs. DVD sales are giving way to cheap streaming/rental. Where retailers were selling VHS or DVD for $5-50 a pop, those sales are being replaced by rentals at $0.50-$5 per viewing. People aren’t watching much more, but they’re paying 1/10th to watch.
The point was that the quality of movies has nothing to do with that.