Depends how you look at it.
If they have a pair of very good dogs, from a very good line . . . . . and want to keep the line going, and take a pup from them, they need to do two things.
Sell the surplus, or cull them.
Both have their own obvious issues!
I've never bred a litter, where all the pups and more have not been spoken for.
But can imagine, a situation where I had six or so homes and the bitch did something daft like drop 12 pups. . . .
I'd end up having to sell a couple. . . . . but i certainly wouldn't chuck them up for auction at the local mart!