The short answer: sexism and money

The long answer:

Sexism: Women’s clothing is seen from an aesthetic view and not a utility view. Women’s pockets give us independence and since women were seen as property for so long, we did not need pockets to hold our items. Men’s clothing is about utility and practicality because men need to hold important items in their day to day. Women’s clothing is seen as just about fashion because women just want to be pretty, which reflects how some view women’s place in the world “be pretty, attract man, find husband, make babies”. Fewer pockets means women have to carry more with our hands which leads to less freedom of movement and less independence.

Money: Fashion companies make tens of billions selling women purses. If women had real pockets, we may not need purses. This is also why fast fashion is aimed at women, our clothing is of lesser quality so we are required to buy clothing more frequently. Women’s clothes are considered a loss leader to sell more cheap accessories.

The thing is, instead of arguing that women don’t really want pockets, you should listen and acknowledge what we are asking for. Times are changing, pockets are becoming larger in women’s clothes because women are demanding them, because we are being more selective and purchasing the few options with pockets that we have. Not as many companies are taking advantage of that ask because they want to sell purses, but the change is happening. You should also be advocating for that change.

The book I linked to above goes into great detail about the history of pockets in general, then provides information on why women’s pockets not only don’t exist as they should, but have actually been taken away from us as we gained independence (during WW2 when women had to work because men were fighting, women’s clothing had more pockets). If you don’t want to read the book, here are a number of shorter articles that provide the same information.

https://www.wtae.com/article/the-pocket-problem-why-women-demand-more-better-pockets-in-clothing-for-equality-and-safety/36327110

https://lifestyle.howstuffworks.com/style/fashion/trends-looks/pockets-womens-clothes.htm

https://luxuryandfamous.com/why-do-women-not-have-pockets-in-pants/

https://mamafashionista.com/why-dont-womens-clothes-have-pockets/

https://fashionmagazine.com/style/womens-pockets/

Great quotes in the above article: Though perhaps no one has put it better than Indiana University professor Christopher Todd Matthews, who writes in the academic article “Form and Deformity: The Trouble With Victorian Pockets” that Victorian women were told that they “had four external bulges already — two breasts and two hips — and a money pocket inside their dress would make an ungainly fifth.”

“Essentially: Men are required to act and therefore need practical clothing. Women are expected to simply appear and be watched — their beauty prioritized above all else. And these outdated gender ideals are still being sewn directly into our clothing”

https://www.thelist.com/176777/the-real-reason-womens-clothes-rarely-has-pockets/

https://www.timesnownews.com/lifestyle/fashion/the-real-reason-why-pockets-are-always-missing-from-womens-clothes-article-151682617

https://www.dailyfashionclothing.com/archives/13499

https://badgerherald.com/artsetc/2022/09/25/in-the-pocket-of-the-patriarchy-history-behind-the-absence-of-pockets-from-traditionally-female-clothing/

https://english.elpais.com/lifestyle/2023-10-10/its-got-pockets-why-this-is-still-a-battle-cry-for-women.html