Fees can be quite expensive
especially if the starting price is high, and the seller just keeps re-listing over and over
many collectors are drawn to the volume of notes listed
Sometimes -- but then it can also be easy to miss something because there's so much to view. Sometimes the inundation of filler is a big turn off to the more serious collector.
Personally, I've never found the 10 cent insertion fees (or other promotions) that big of a draw because my item is suddenly competing with 2000 listings instead of a 1000. Also it could be only the cheap guys checking the item out. Most often these so-called "breaks" are given when sales/volume is at a low. I doubt there's any public advetising campaign to bring in new viewers/bidders, or to really stimulate the market.