Easy. Maybe they need $141,000.
Or maybe the house is worth $150,000 and they know it, and won't take a penny less than their asking price.
Or maybe your offer had some other terms and conditions that made it less desirable--that they couldn't accept a weak offer at $140,000.
Maybe they considered the $141,000 a teaser price, and anticipate a bidding war that will push the price higher.
Maybe they're the sort of seller who gets "insulted" (I hate that term and that concept) at any offer lower than the list price. I answer questions on Trulia all the time from buyers who ask about lowballing and my answer is: You can't read the seller's minds. One seller might be delighted at an offer 15% below the listing price. Another might decline an offer even a penny less than the listing price. You don't know.
There are lots of other possibilities, too. Ask your Realtor for guidance.
Hope that helps.