My guess is because someone handicapped might have their hands full with their chair/crutches/walker that they make an easy target for something like a purse snatching. Also you can usually spot them coming out of the store so just before you break their window glass you can glance at people exiting the store and see that none look handicapped and bet that they are not going to be walking toward the car your about to hit, so the smash and grab crimes are easier.