coming from someone with a history in banking, specifically complaints....
I always got the impression that people with joint accounts where either A) Whipped or B) Absolutely ancient, one partner still keeping money under the mattress etc.
There is literally no reason to have a joint bank account these days, unless one partner is paranoid to the extent of needing to look over the other's spending, by this point whether you have a joint bank account or not is the least of your worries.
Plus joint accounts can cause sooooooooo many problems when a couple breaks up. Any money spent by the other partner is no reclaimable, all bills and charges are legally spread between both parties regardless of who caused them. A partner can legally take all the money out of the account and then close it, the only thing you can do is set it up that both people have to sign (or give permission) to close the account, which doesn't stop the money being taken. Although banks do have marital dispute blocks, an individual is legally entitled to remove all the money up until those blocks are placed. It's easier via a divorce/separation to claim money via their own personal account than via a joint account.
The amount of times I had to deal with crying or distress people who partners had left them (one time had a crying wife whose husband had left her for a random woman) and emptied the joint account. Left pretty much penniless, needed to be given debt support, couldn't delay any payments for overdrafts etc as she had none and nothing we could do to help her as we where not liable (aka banks are only liable to help people who owe them money). Imo anyone who sets up a joint account is an idiot.