I make all of my own buying decisions because my wife trusts my judgement.
My wife and I always go grocery-shopping together - because, if I went alone, I would buy the wrong brand / kind of "sanitary napkin" (Is there really a difference between "maxi-pads," "tampons," and "shields?"), and if she went alone, she would buy the wrong kind of whiskey ("Well, isn't vermouth a kind of whiskey?!").
Regards,
Haha! That made my night.
I do the shopping, mainly because I pass right by the supermarket on my way home from work.