I've never been a fan of purses, cause of then having a hand/arm occupied just to carry the damn thing, and the high risk of getting it snatched, or simply forgetting it somewhere. However shoulder bags I do use frequently, especially cause I need to carry around more stuff than I can reasonably fit into all pockets available on both my pants and jacket together... I've also lost things I've carried in pants pockets cause of them falling out, so that's something I've learned to not do anymore.
For me I don't just carry wallet, keys and cell phone. But also cigarettes, lighter, extra lighter, headphones, handkerchiefs in masses, somewhere to put used handkerchiefs, glasses, sunglasses, cases for both of those, a pen of some sort, a writing pad, painkillers, bottle of water, etc... So I need a big bag!
I don't know if shoulder bags are all that masculine, but they do give me the impression of being generally gender neutral. I also like being able to have my bag wrapped securely around me and have it in full sight at the same time. Mine is entirely black and I've sewn on a couple of patches. One says "goth as f***" with a white print of a skull and the other is a small "pride" patch in rainbow colours. And I attached a bat (the animal) shaped reflector to it as well, and a keyring depicting a miniature whiskey bottle. So it's not overdone, but it's a little out there.