As @Drago point's out most of the time you are not dealing with Raffles. Often simple stuff get's them spending time in the cell's. The one thing most value is getting away with it. Quickly bag 5 unlocked/ simple locked bikes with little chance of getting seen say over 1 hour. Or spend 30 mins trying to get hold of one with a better lock but with bigger risk of getting seen and ending your hour in the cell's. That's about as complex as the thinking get's for most of them.