I'll cite two examples of "why not". When the WolfSpyder was released, I was interested enough to go to Ray Mears website and price it. At the time, it listed there for $279 plus international shipping to get it back here, which was out of my price range. At the next Seconds Sale, I happened to see someone snag one out of the trays and drop it in his basket. My eyes followed that green G-10 and saw a half dozen more of them in his basket. When I asked if he was planning to buy all of those, he replied "No, you have to try a bunch of them to make sure you get a good one." Every person I saw with one had four or more in their basket to sort through. Every time I saw that, I thought "You're getting a $300 knife for $85 and you're being picky?" Yes, they are.
Second example. At another Sale, I was proxy shopping for someone else and managed to find a lefty Military. The ladies at the checkout were surprised to see it, saying there weren't many of those out there. The person I bought it for sold it on when he wasn't able to correct some issue that I didn't even notice while examining it first hand.
These knives didn't pass QC for one reason or another. Even if the took and posted 20 pictures of each of the several thousand knives at the sale, you still wouldn't be able to feel the action or check for blade play.