When travelling I usually have a heavy DSLR and lenses, ipad or guide book, sunglasses, reading glasses, ordinary glasses, sunblock, hat, jacket, tissues, heavy wallet, insect spray, keys, phone ... a bag is simply easier.
What irritates me is not so much the lack of pockets on women's clothing, but the fact that his nibs can pop his wallet and passport in his pockets and then ask me to carry his shit for him in the bag (rucksack) I invariably take or rely on me for tissues, sunblock, etc! (Usually, I say 'no').