Well friend, it is not a question of why do you NEED another one. It's more ofyou WANT another one. Of course that is if you can afford it. Its obvious you have other obligations and priorities. Also you need to 'save for a rainy day' too. But when all is said and done and you have the extra cash then you and your better 1/2 should share. And maybe even include a nice dinner out.
Also, you can check the used racks out and tell her - "look, I can get this one and save $x.xx over a new one." Remember you can catch more flies with honey than with crap.