I believe the purpose of the show is to add some sort of humor to death and finding criminals. It gives us the change to look at detective work in another way. This show is not obviously set with a real world scenario. If it was Shawn and Gus would of been long gone by now, but because they almost never get hurt it gives them the look of having control of the situation By having this some sort of a 'force field' against the characters and the added humor, this makes this show perfect for all ages. Different generations should understand the different type of jokes they put into it making it entertaining to all. Also the crimes that they solve are not as complicated as normal making it easer to understand for the younger ones, but hard enough so the adults don't get bored.
Even with a gun around his neck Gus was still able to survive and bring the bad buys down with Shawn.