So, you're just assuming they're old…
i've met many, and they were...let's say in their 60s...
You don't believe that some retired police officer at 65 could do the job?
protecting all the houses in the gated neighborhood? well, lets just say that he wouldn't be efficient... and, sorry, but no young men wants this job anyway...
and don't tell me he walks around (or drives) your block to check if all is alright... they sit in their little booth, eat sandwiches with hot tea and watch tv... but you don't know it because you're at work... :)