I just went into my account and checked... If you don't accept a bid, it automatically rejects it after 72 hours. What is the point of accepting a bid below you

I just went into my account and checked... If you don't accept a bid, it automatically rejects it after 72 hours. What is the point of accepting a bid below your reserve price or expiring bids after 72 hours on a 30 day auction? Lots of messages from users wanting to know why I "rejected" their bids and I didn't know what to tell them. I understand measures to prevent artificial price inflation, but anytime bids started becoming competitive, they would start to expire.