Why are there so many unopened amps, ect for sale?

I've noticed a lot, lately, especially McIntosh, ads for new amplifiers, preamps, ect in boxes never opened by non-dealers, just "regular" people. Are people hesitant to buy these. I myself was looking at a new McIntosh MC352 amp from a private seller. He said it's new and the box has never been opened. I'm rather hesitant to buy it, because why would someone buy it, never open it, and then turn around and sell it? I'm just curious. If it is truly new, would McIntosh warranty it; I'm assuming not since it's not coming from a dealer even though the warranty cards are supposed to be inside the unopened box. I truly would like to buy this amp, but am hesitant, and I'm wondering if anyone else has wondered why there are so many unopened boxes of stereo equipment for sale by non-dealers. Usually when we buy equipment from this site we know it's used equipment, unless it's coming from a dealer. Just a curious question and wondering if anyone had feelings on this subject. Thanks.