It's the inequity in pocket sizes, the OP said. Women don't seek out jeans with small pockets, but the pockets on women's jeans are just smaller as standard.

I can't say I've rooted around in my boyfriend's pockets enough to make a comparison, but it's completely true to say a lot of women's clothes just don't have pockets at all. The love of cargo shorts aside, they might not be quite suitable for every occasion.