Answer:
Because in one way or another, you would lose money.
Explanation:
Sometimes, it is a good idea to underprice a house when selling it, specially when there is a hot market to start a bidding war. If this is not the case, when the prices go down, it means that the seller must adjust his prices to the market; meaning that the lower the prices are, the lower the underpricing should be, so the seller would lose money.