I get asked this all the time; should I rekey my locks when I purchase a new home? I explain the security issues associated with not rekeying your locks after a new home purchase. Many realtors will leave keys out under doormats for perspective to view after hours. Or the existing homeowner might have keys scattered between family and friends.
Who knows where keys maybe over the years of home ownership, so it makes good sense to rekey your locks and give you and you're a piece of mind when you move into your new home.