How do you millions of Americans survive encountering unknown dogs each year without resorting to shooting them? What makes the cops so different that they can't respond like a normal human being?
charlequin already answered this. But I still say it's because most cops want to eliminate risk before it happens. Problem is, they are supposed to be getting paid to do a job that has risk. Even simple things like detaining people. They always seem to go to the extreme and use harsh measures to negate any and all risk that might come to them. This kind of mentality is easily abused too.