True. But they're unguided, almost none of them will cause real damage, but you have no choice but to take all of them out to prevent the losses from a lucky shot - at great expense. It's a great way to drain your enemies funds, great asymmetric warfare. Casualties are just icing on the cake.
Part of Iron Dome is trajectory analysis. If the profile of a target matches that of an unguided rocket and the CEP is in some unoccupied area, no interceptors are fired. If it looks like it'll land in a populated area, interceptors are fired. It doesn't just shoot everything in the sky.
