Because if it actually takes an hour to crack your lock, the police eventually happen to drive/walk/horseride/bicycle by. Those horses are huge btw, and when did BMW start making bicycles?! Sure, you can saw through a lock in an hour. If the police drive by and see you, they will stop.

It's also a large psychological deterrent. Outside, at night, under the cover of darkness, you can do some seedy things. If you get caught and run, maybe the darkness prevents identity. It's a comfort blanket. Now imagine doing those seedy things standing under a 2000 watt sodium lamp that lights up a 15 foot diameter area as bright as the sun.

By the way: Cherry picking.