My opinion is not unique, but women are not given many choices about fashion and pockets or lack thereof. You can say to vote with your wallet, but it's hard enough to find clothes that fit properly (I am both overweight and have a very small waist in comparison to my hips, finding jeans that fit over my butt without having like 3 extra inches in the waistband is near impossible), without having to exclude jeans that only have back pockets.
Every woman loves an outfit that manages to be cute and still have pockets. It's like the holy grail of womanhood.
It's really nice to be able to leave the house without a goddam purse. Tuck a credit card, a $20, a metrocard, a phone, and keys into your pockets and go for a walk in the park with your hands and shoulders completely free and unweighted.
Oh, and a phone in a purse? Harder to hear ring or beep, and you sure as hell won't feel it buzz.
And that's before even mentioning one-handed use, which as someone else pointed out above, is crucial when you have to hold a subway pole or carry groceries.
Women carry purses? Men carry backpacks and messenger bags. They still put their phones in their pockets and get annoyed when they can't. Or would you say it's ok for a phone to bend when you leave it in your pocket because you could just carry it in your backpack instead?