It isn't stupid it is just an extra protection measure for the seller that attracts more sellers to eGay. I believe you have to pay a little extra in service costs to eGay for it though. It means that the seller can set a certain price (we will say $120 for example) so that if it doesn't reach that price the seller has the option to not accept the auction results. That way the seller could, for example, be sure he at least got $15 more than he payed for it.
That is just one part of why I personally do not usually even visit eGay anymore. By the time most auctions end the price almost always ends up being what you could buy it at most online stores. The Hot Deals forum has been my primary means of saving money.