New pickup / why was this so difficult

[bbcard1]

I was able to pick up mid-grade 1970 and 1971 baseball sets after a fairly considerable amount of looking. I originally collected them as a boy and I am sure I have never parted with them, however, they have gone AWOL. I suspect I'll find them at some point...but that's not the issue here.

Why is it so hard to find collector grade sets like this? When I owned a shop, there was virtually always someone coming in working on a set from the 50s, 60s, or 70s.Of course if I wanted to pay two to three times value, they are always on eBay. These very seldom come up for sale, say in an auction setting or at a reasonable price from a dealer at a show. Now you run into high grade fairly often. Why do you think this is? 1) are dealers purchasing the sets and breaking them down into singles or 2) are the collectors simply holding on to the sets?