Haven't you heard of people stacking fiat in their homes and not the bank?

When you choose to stack fiat in your house and not the bank, it is called self custody, however when you save it in the bank, you give the bank custody.

When you've the keys to your personal wallet, it's called self custody. When you trust a centralized service with the safekeeping of your funds, you give it custody. So what are you talking about?

The advantage fiat has over crypto is that most elderly persons and illiterates will have difficulty in interacting and securing crypto.