While that rule works in some places, part of the story with Mexico Beach is that it is (was?) the start of the poorer, quieter section of the Redneck Riviera. and the area had been lucking in avoiding past hurricanes to strike the area. Florida's gotten better with code enforcement, and between that and dollars being drawn to the beach, newer construction does a better job of standing up to hurricanes than older construction, all other things being equal. (Of course, even then, not much stands up to 135 knot winds.) You could really see this with Opal and Dennis. So with older construction not having been wiped out by a major storm previously....Mexico Beach was particularly bad.