Many reasons come to mind, such as not wanting to live in the area you work (maybe you have kids the schools are bad, or the neighborhood isn't real good). It could be that living close to a family member is more important than living close to where you work, like maybe your wife is taking care of her mother or grand mother while you are out working (or the other way around).

There are lots of good reasons. These days you just might be stuck in a mortgage because the value of your house has fallen below what you owe. Given the current "economic climate" it's very easy to have gone from a 70% LTV to 110% LTV.