The most notable feature of joint tenancy is that when one owner dies, the other owners automatically inherit the deceased person's share of the property. But if you become incapacitated, the other owners have very limited authority over your share of the joint tenancy property. For example, if you and someone else own a bank account in joint tenancy and one of you becomes incapacitated, the other owner is legally entitled to use the funds. The healthy joint tenant can take care of the financial needs of the incapacitated person simply by paying bills from the joint account. But the other account owner has no legal right to endorse checks made out to the incapacitated person.
Matters get even more complicated with other kinds of joint tenancy property.
Real estate is a good example. If one owner becomes incapacitated, the other has no legal authority to sell or refinance the incapacitated owner's share. The expense and intrusion of a conservatorship are rarely desirable. In a few situations, however, special concerns justify the process. A conservatorship, with the built-in safeguard of court supervision, is worth the extra cost and trouble.