You need to keep things off the books sometimes. Try saving up for a significant other's gift, if you can't keep a few things hidden.
We have a joint credit card but I don't see why we'd ever need a joint bank account.
We have separate bank accounts and credit cards and we split the bills most things, like groceries. But we don't look into what personal purchases we make, for example me buying Lego.
It's pretty easy to decide if we should pay together or not. At least for us.
That way, you never have to deal with splitting shared expenses, there's no worrying about who's earning more, and financial decisions are by default made together, but you can still buy your LEGO with your own money.
It's fine to have a joint account that you pool part of your income into. But there is no reason not to have a private account as well. And trusting someone doesn't mean having to completely expose everything to them. Just because I trust someone, I won't let them snoop through my phone, hand out all my passwords, or give them 100% access to my bank account.
Trust also means to trust someone enough to let them do their own thing.
After all, if you are married you are jointly and separately liable for all assets and debts so why doesn't your banking arrangements reflect that fact?
In countries with matrimonial property regimes, that isn't necessarily the case.
This is a problem in cases where (typically) a husband is abusing his wife, by withholding her access to the funds unless she does what he wants.
The solution which is finally being looked at is to revert to paying each person their benefit entitlement separately.
That's not even something the abused spouse can choose for themselves because they "don't trust". It requires the state to recognise it is important to treat each spouse separately, automatically for all of them, to limit the possibility of abuse via joint accounts.
Just as importantly, I can't imagine that I would have zero chilling effect on my spouse either. So even if they preferred a joint account, I'd insist _they_ have a private account that I couldn't see as well, and that it had some liquidity in it.
It is important to me that my spouse feels as free as possible, and that they have some personal life which is just for themselves, outside of my view.
Post Zelle? I dunno. The last time I just wrote a check.
A direct transfer from online banking might take overnight or over the weekend, but there is an app that lets folks pay each other that is low-cost and speedy (or pay for a soda from a machine).
Everyday spending is on the debit cards, and immediately visible in our online banking apps.
Birthday presents and things we want some privacy about go on our individual credit cards, with just the total monthly repayment visible in the joint account.