The hotel's elevator has a neat security feature: It only accepts keystrokes to the upper floors, if the key card is inserted. At least as long as the elevator is not on one of the upper floors, then it accepts anything. Well, find any person moving towards the elevators, join her in the elevator and simply wait until the elevator reaches sufficient altitude to go anywhere you want.
This feature obviously serves to ease the life of the guests, for otherwise they would have to enter their key-card anytime they'd go to the pool. Well, would that be inconvenient. And as any distinguishing security scheme ist too hard to implement for the average elevator-builder we leave it as it is.
Lesson learned? Don't make things too comfortable.