Wills can get complicated. Especially when the person is dead. Blockchain uses hyperledger which is like a public receipt. If there's a clear and easy way to make a will and update it then there will be less confusion. It will also lower the barrier of entry to make a will. Do you know how to make a will?
Also people who make wills typically have money and/or valuable assets. So your users have money to spend on the service.