Yeah, right? I thought this was settled at least five years ago. Preface: I get we're not in a frictionless vacuum free market with perfectly rational agents acting on perfect information. Auto makers in the US, for example, induce demand for massive fuck-off pickup trucks – which exploit regulatory loopholes and are worse than standard cars for most people – by driving down the supply of alternatives and massively marketing trucks to people who categorically don't need them.
However, pants are an obvious case where you can't have both: you can't have normal-sized pockets (let alone the Felix the Cat-ass ones men can have with cargo pants) and elegant, form-fitting clothing. Demand always exists for big pockets because big pockets are objectively beneficial, but at a population level in a zero-sum game, women prefer form (fitting) over function (bigger pockets). This does leave a minority who actually would prefer and buy the larger pockets, but because this is a minority, it's also the minority of supply, and these women are faced with fewer options. Because the supply of pants is highly elastic, the amount of pants with good pockets is probably close to its actual demand – even accounting for imperfect information where some women may truly want but just not know how to buy them. It's also true that demand for bigger pants would go up if purses weren't so normalized among women, but they are, and there's not a strong force acting to reverse that.
On a personal note: I don't get what the big deal is (I mean I do, but not from what I'd see myself wearing); the women I've known who wear looser pants with baggier pockets to me have usually looked better.