In reading what both kittenfemme and Jane have posted, it seems to me that a contract is great for those short term relationships, as in one that is not permanent.
This may not be true in all cases though.
I guess since TG and I are married and neither of us is going anywhere, there really is no need for a contract. I think I may find a contract too restrictive in a sense for our relationship is constantly changing due one circumstance or another and a contract would be too binding for either ofus.