[timv]

Others have mentioned the importance of joint savings accounts for married couples, and for businesses.

They're also very important for mortgages. If the mortgaged asset is jointly owned (and that's typically the case in a marriage) then you, in practice, need all owners to be a party to the loan. The house is security on the loan - if I only own half the house then I can only borrow against my half. And my wife can borrow against her half. But if I default on my loan, then how does my bank foreclose on me and sell their asset when there is another owner who may not wish to sell.

There are other solutions, but the easiest, and the one that banks will typically insist on is a joint asset requires a joint loan

[adebtlawyer]

People rarely think of this in advance, but joint debts of any kind usually become a problem in divorce. One former spouse will stop paying and ruin the other spouse's credit, to say nothing of causing foreclosures. It doesn't matter what the family court orders (this spouse will pay that debt, etc), because that won't change the underlying obligation as far as the creditor is concerned.

Joint credit cards, which aren't attached to any asset, don't have much benefit compared to this downside. What people are typically told is happening is that the credit card still 'belongs' to one spouse, but the other will be also authorized to 'use' it. While this is possible, the paperwork presented to sign often makes the other spouse jointly liable for the debt instead. I'm convinced even the bank representatives don't know they are setting up things this way and are just following a script. You have to read the paperwork to see what it does.

[stephengillie]

This is exactly where I was leading with my questions. Joint accounts might simplify the sharing of cash between household partners, and thus simplify household operations, but it complicates everything else.

I suppose a temporary convenience now is worth a very complicated situation in the future. Thus is also why we traditionally forego prenuptial agreements.