Why do girls carry purses?

I am a boy, I have pockets and carry my phone in one and my wallet in the other whenever I leave the house.

Why do girls carry purses instead of putting stuff in their pockets? Won't they forget their bag somewhere? What is even in this bag? My girlfriend carrys lip balms, tampons and a comb but I tell her she does not need to, as they are not necessities. I never see guys carry lip balms, plasters or a comb. I think nearly every girl carrys a purse.