Yeah, it's because big pockets would look "bulky" on tight pants that are meant to show off the body shape. Women's clothes are usually "looks over practicality" while men's clothes the other way around. Women are also more encouraged to put their stuff in bags instead of pockets. Or, alternatively get the men to carry their things for them. At least that's common among straigt couples, I've noticed.
However, women's jackets often have quite decent pockets. Although depends on the style of jacket, but parkas, trenchcoats, some leather jackets, etc usually do. I've a parkas that has 4 very practical pockets and I love that jacket, and although it's not very feminine it is intended for women to wear. It looks unisex though. I've had it for the past 17 years now and it's my very trusty jacket that's been with me through childhood to adulthood, through transition and detransition. And somehow it still fits me. It's just something special about it!
So I usually put my phone and wallet in my jacket pockets instead, if I don't use my shoulder bag for that. And if I'm not wearing a jacket or I'm indoors, then a cardigan with pockets on is very neat. I also stick my phone into my bra sometimes when I use it for listening to music and the headphone wire is short. I don't have boobs but wear breast forms in pockets of mastectomy bras, so I then put the phone basically between my flat chest and the breast form. The phone falls out when I lean forward, but if I don't do that it stays in place.
However I don't usually wear pants at all, as I'm much more comfortable in skirts and dresses instead. Those rarely ever come with any pockets at all. At least not the styles I go for. So that's even more of a reason for me to rely on the pockets on jackets and cardigans. For outfits that have no pockets at all though, I actually wear a waist bag. I've one made of leather in an antique style and with a brass lock-thing. I bought it at a medieval market some years ago. It works with any kinds of belts and I just about fit my samsung smartphone, small wallet, lighter and one pack of cigarettes in it. My keys I have to find another place for.
