That's a silly statementNo, it's silly to assume that your experiences are the only experiences that exist.
Nearly every woman I know carries it in the back pocket of her jeans/pants
Most of the women I know only wear jeans on weekends. And some, not even then. I don't own a pair of jeans at all. My wife has one that she breaks out for Halloween or gardening.
Some will also carry it in their purse when her clothes don't have usable pockets.
Some women can't carry a purse with them all day to stick a phone in. For example, shopgirls in high-end boutiques, who can't hold a purse while doing their jobs, and also wear clothing that more often than not does not have pockets.
At one time Burberry made a cross-body purse that was just a strap and a tasteful phone case. It was very popular among the class of women for whom jeans aren't a fashion go-to.