On the one hand, girls have more things, especially cosmetics. There are also some girls who like gadgets. It's inconvenient to put everything in the pocket of clothes and trousers, but it's more convenient to carry a backpack. Especially in summer, most of the clothes and skirts that girls wear are simple in design and have no pockets, but when they go out in summer, they basically take a bag with some wet tissues, dry tissues, a small fan and a mobile phone.
On the other hand, girls' backpacks can play a decorative role, and carrying a suitable and beautiful bag will make the whole look harmonious and icing on the cake.
I feel that regardless of age, girls are willing to prepare a backpack for wearing and going out according to their own needs for convenience and beauty.