Your area may be different, but here in Southern CAlifornia, only dive classes use a dive flag. Experience in the community has been that since, for some strange reason, we do not require licenses for boating, any one can get a boat and take it out. All too often dive flags are not "Keep Away Diver Down Stay Clear 100 Feet" but are more of a "I wonder what that is? Lets go see" or a Salom course for jet skis.
We just dive with no flag.
We just dive with no flag.