The point is not the occasional buying of socks for one's partner. The point is that for some couples, women do all the buying of socks, pants and so on. And I have never, ever seen this going the other way.
probably to do with the fact that a lot of men (my DH included) wears a lot of the same stuff - always the same jeans, same style of shirts, same socks and pants. it is therefore very easy for the DW to buy clothes for them. Women's clothes come in a much bigger variety and styles effect sizing etc therefore much harder for a man to shop for a woman IMO
I make DH's lunch as well as do his shopping, I'm making the DCs anyway so it would be silly not to just make his at the same time.