I keep trying to get my husband on board with learning how to handle finances or at least know what is what. He finds it easier to just get an allowance and then ask me if we have enough money to get things if he wants something that costs more than he has in cash. I'm mentally going because he's going to need to know these things when/if I die before him.
The various stories of one of a couple being clueless about finances or other practicalities, and totally dependent on the other for same, bring to mind a dear late uncle and aunt of mine. They were both lovely people, very happily married for fifty years; he was a dreamy, vague character with considerable artistic talent, she was the one with the practical abilities, who handled all the financial and administrative stuff, in which he was totally uninterested and which he was very happy to hand over entirely to her, and himself know nothing about it. (There is an innumeracy gene in our family -- I'm terrible arithmetically, but my uncle was beyond terrible: on a good day, he could add 2 + 2 and maybe get 4 as the answer, twice running.)
For some reason, my uncle was convinced that he would die first, out of the two of them. Unfortunately, that was not how things came about -- she predeceased him by some five years. That last half-decade was for him in many ways a confused, unhappy time -- he was in his mid / late eighties and his mind was no longer serving him all that well. We all helped him according to our ability: relations and friends tried to teach him such things as how banks worked, how to write a cheque, and so on; but it was a losing struggle for the poor old guy. If people as a whole were more sensible, they'd take thought as to how they would cope if they were left on their own; but very often, people just "don't do sensible".