A Durable Power of Attorney is still needed even if you are married. Your spouse can not automatically act on your behalf just because you are married.

For example, your spouse cannot name or change beneficiaries on your life insurance policy or your retirement accounts unless your Durable Power of Attorney specifically gives your spouse this power.

Another example, is that your spouse cannot sell your jointly owned home or property because you have to consent to the sale. If you are incapacitated and your spouse does not have Power of Attorney to perform these duties then your spouse will have to obtain a conservatorship over you in order to proceed.