how many people walk around with body armor on? and how many of those people are gonna rob you or a store or bank etc... getting ahold of body armor in the first place can be a hard thing to do... and it isnt cheap... sure someone who thought it out and had intelligence would think gee... before robbing this store i should get some body armor... but if they had intelligence in the first place they would have other means of income.. however if body armor truely threatens your means of stopping an attacker get a bigger gun and/or armor pierceing rounds...
and as a side note... ive seen a deer wearing body armor !!! why do you think hunters need such big guns ?!?