It's sometimes easier for dementia sufferers not to deal in cash. My MIL is a case in point. She was terrible with cash. She'd constantly get a bus to go to town to withdraw cash from her building society (sometimes daily as she forgot she went the day before). She also had several different accounts, one in which her state pension was paid, another in which her occupational pension, then two accounts out of which came direct debits. So she also kept going to make transfers between accounts. She hadn't a clue what she was doing, but it was a small branch, and the staff knew her, so they'd do the switching for her and just get her to sign the transfer slips!
Then she'd hide it all over the house because she was paranoid about being robbed. Next day, she'd open her purse to see nothing in it, and would trot off on the bus again. We looked at her passbook and she was withdrawing hundreds every week - yet she still had nothing in her purse. She was convinced people were coming into her house and stealing it! In reality, it was all over her house, in the fridge, in the bottom of cereal packets, under her bed, in her bed, tucked down the back of the sofa, in the microwave, in pockets of clothes in her wardrobe, etc. We had a real good look around one day and found several thousand pounds in total, which we took back and banked again!
It was all such a mess and MIL hadn't a clue and was getting constantly stressed. We closed all the accounts and opened her an account with the Halifax - a simple current account, all pensions paid in, all direct debits to come out. Took her about a year to "get it", and she continued getting on the bus to go to her other building society, where they kept telling her she'd closed all her accounts - apparently she sometimes got aggressive and accused them of stealing her money, but they were very understanding and phoned us a few times to tell us she'd been in again! After a year, she'd basically forgotten about the banking fiasco, and her Halifax account needed no attention as the money in was more than enough to cover her direct debits, so she could happily ignore it.
At first we'd take her to the cash machine to withdraw a bit of cash to keep her happy so she could pay her papers, buy a few groceries from the local shop, etc., but over time, we got her used to using her contactless debit card, and now she's in the habit if just swiping it at the shop. She literally can't remember any other way. It's so much easier, and she's not constantly roaming about and getting stressed trying to deal with cash! Now she just doesn't have to think about it at all.
So I don't really understand why so many people think dementia sufferers can't deal with a card - it's a hell of a lot easier for them than faffing around with getting cash out of the banks, potentially losing it, thinking they're being robbed when they lose it, etc.