It is meant to be a deterrent. The problem with deterrents and "security theater" as it's called is that you can't measure its success. If it works, then nobody ever finds out because it stopped something from happening. Thinking that lack of finding things makes these measures worthless is flawed logic. We'll never know if someone decided not to do something because these measures are in place. Yes, there are ways around every security measure and nothing will stop a person who is determined enough, but that doesn't mean that you shouldn't implement the basic security measures.
Think about it like this, to get into a house that has a door with a deadbolt you could pick the lock, ram the door, kick the door in, shoot out the lock, melt the lock, break a window, drive a tank through a wall, and I'm sure a million other likely or unlikely scenarios... I'm still going to lock my door tonight.