While reading Mother abusing my finances (and others like it in the past) I always remember when I opened my own checking and savings accounts as a 13 year old. No adult involvement at all, except for driving me to the S&L. That was, though, many decades ago.
When did that change, and why? (I'm guessing it was a side-effect of regulations enacted to help prevent money laundering, terrorism, etc, but am not sure.)
It may be related to the country concerned in the question.
I've done some quick googling and it seems in the US, a parent needs to "own" the account.
Myself in Canada, I opened an account when I was 16; although my parents were present to sort of sign some papers, the account was in my name, and I would be responsible for any minor problems. "major" problems could not be a thing, as if it exceeded -100$ in "issues" (dept or fees, or stuff like that) my account would simply be closed and wait for my 18s.
I've found an article from the Canadian governement's website over accounting which states that in Canada, any citizen over 12 years of age are allowed to open and own a bank account.
In the US, it seems you still can, but you do not "own" it; but I havn't researched much on the US side of it, on the "how much of it you own" part.
Couldn't find "when". I havn't researched much but couldn't find when it was a thing and then wasn't; maybe it's something between states?
The earliest (reasonably authoritative) statement of general legal practice in the US that I found was The Restatement (Second) of Contracts, specifically ยง 14:
Unless a statute provides otherwise, a natural person has the capacity to incur only voidable contractual duties until the beginning of the day before the person's eighteenth birthday.
It is not legal code, but may provide a sense of general acceptance of this practice in case law. The treatise was written throughout the 1960s and 1970s. The question of a minor's capacity to enter a contact is certainly not modern, going back to at least the 19th century.
Once you have this precedent in place, it seems reasonable that banking institutions would want to protect themselves. Note that it doesn't prohibit the bank from entering a contract with a minor, but the contract is generally voidable by the minor. (Eg, minor doesn't maintain account balance requirements, bank levies fees, minor voids contract to avoid fees).
I don't know if this is the actual basis for the shift in practice, but it seems a reasonable explanation that somewhat fits the timeline in your anecdote.
