I have a debit card on the way, and want one for my wife too.
Sure, she could open up her own xapo account and apply for a card, and we're willing to do that.
But if there is no way to link those two accounts together, so that they have a shared balance, it becomes too much of a hassle.

Let's say her account holds 300 dollars worth of bitcoin, mine 500. Neither of us is able to buy something with our card which costs 650 dollars.
But if the two accounts had a shared balance, we would have 800 dollars. See my point?
The way it is now, we would have to move funds before making said purchase, which seems inconvenient.