If for no other reason, you need a will to name an executor (or executrix).
So, do you really need a will? Yes. Really.
A recent Forbes article titled "Do I Really Need a Will?" recommends that you should have a will to at least designate an executor or executrix to administer your estate. This individual will be responsible for taking care of your affairs after you pass away. Without a will, the probate court will appoint an administrator—this could end up being almost anyone. Anyone with a decent reason has the ability to petition the court to be appointed—like your cousin Reggie (who you last saw at your fourth birthday party) or your Uncle Ted (who is always dressed like it is 40 below, even in July).
Why even tempt Reggie and Uncle Ted? Name the person you want in your will. The executor or court-appointed administrator will identify and gather your estate assets, pay off any outstanding debts or taxes owed by you, and distribute the remaining assets to those designated as beneficiaries.
If you do not have a will when you pass away, the probate court in your state of residence will decide who gets the assets in your estate through its intestacy laws. Typically the assets generally pass to the immediate family first (spouse, children or parents). However, if you are single with no children or surviving parents, the state will distribute your assets to your remaining relatives. For example, this list ordinarily includes siblings and their children; then any grandparents, aunts, uncles and their children and grandchildren. If you have none of the above, then your estate may pass (“escheat”) to your State or Commonwealth.
So you see that Reggie and Uncle Ted still could get in there for some of your money, if you fail to draft a will with your estate planning attorney.
Reference: Forbes (August 19, 2014) "Do I Really Need a Will?"