There are lots of reasonable uses for flathead screwdrivers other than driving screws, though! Random examples:
* Many clips (dryer faceplate, window sash, ...) are designed to be pried open with a screwdriver.
* When repairing a popped drywall nail, a screwdriver is a good tool for removing the joint compound under the nail.
* When you buy a lock it usually comes with a rounded faceplate. To swap the faceplate, they'll tell you to use a screwdriver to pry it off.
A flathead screwdriver is a good tool for general light prying, not just for putting in slotted screws. This heuristic has a lot of false positives.