I think it's because we're younger and the 70s canon is so established. It's just hard to break free of received wisdom on this one.
I'm old and I didn't come up with anything off the wall. I saw all of these movies except for a couple in the theater like everyone else back then. Not too many people had VCR's until the 80's. When we got them and movies became available, they only made VHS movies of the most popular current films. I don't know when they started releasing older movies but it took a while to figure out there was a huge market for them.. Also no one really had cable until the mid-eighties. After cable people started recording the odd, little known, time killer movies off HBO.
If you didn't see it in the theater, you didn't see it.
If it wasn't really popular, I don't think they ever produced it on VCR.
ETA: There are more old movies out on DVD than there ever were on VCR.
This post was edited on 11/1 at 9:59 pm