There are various situations in which a Power of Attorney can be useful.
POA can cover circumstances in which you are involved in a serious accident, or become seriously ill, and either find it difficult or are no longer able to deal with your own affairs. Your Power of Attorney can remain in place indefinitely until specifically revoked by you.
No-one can act on your behalf unless they have the legal authority to do so. They can get that authority through a Power of Attorney, and you can choose who acts for you.
If you don’t have a Power of Attorney, then your friends or family will need to apply to the Court to be appointed as your Guardian. It would be at the discretion of the Court as to who should be appointed as your Guardian, and they would likely require to apply every few years to renew this authority. If the need to act on your behalf happens suddenly, this can cause stress and anxiety, particularly if they are reliant on accessing your bank account for important bills and living costs. An application to the Court to be appointed as a Guardian can take approximately from 6 months to a year.
As well as the additional time taken to be appointed as a Guardian through the Court, the cost of the Court procedure is likely to be many times more than it would have cost to prepare and register a Power of Attorney.