Middle names are often a way of preserving a family heritage (in my case, for a boy, it is William, James and Benjamin). I see it as a nice way to pay tribute to a family member or close friend, or to carry on a family name. Middle names also offer a nice balance between the first name at the surname.

If a middle name doesn't have a family link, generally it has a special meaning to the couple or family.

I don't have very good reasons - but I know that in my case, my son will have two middle names (it's family tradition) and my daughter will have a meaningful middle name - when I eventually have kids that is!