How does the bidder know what the reserve is?

A lot of bidders will not place a bid early in the auction...they wait till near the end and then place one bid...of they win that is great, if they don't win, too bad.   If there is a reserve on the item there is every chance that the one bid will not be enough so the item will not sell.

You are really better off starting the auction at the lowest price you are prepared to accept...in other words, everyone knows the reserve and can decide if they want to bid.