They don't always sell. Still some NOS in the box Raleighs and Univegas popping up on eBay from time to time. Basically, they came in at the end of the 70-80s Bike Boom just as the market was switching to mountain bikes big time.
They are a (so far resistible) temptation for a guy like me who started in the 70s. Kind of like a time capsule.
I'd imagine that 20-30 years from now a NOS Trek or etc. will pop up here or there.