Unfortunately, in many cases, this is due to the quality of the domain name offered. However, more often than not, the zeros are entirely due to the implementation of the eBay auction. In the last three years, I've held tens of eBay auctions, and I sincerely believe that I've never had an auction end without receiving at least one bid. Most of the time the bidding hits the teens, and only occasionally the 30-40 range.
Bids create interest.
When the scanners and speculators get involved, this pushes both the price and the number of total bids upwards. Multiple bids create even more interest. The auction begins to fuel itself. These individuals often include VC firms, companies looking for an online presence, attorneys and consultants looking for the right name for their client. If you don't meet your reserve price, you are not legally bound to sell your property.