Exactly. In the real world, this is likely iterated dozens of times every winter, against neighbors you'll see repeatedly.
In a college classroom, where someone tells you you'll get fifty bucks if you score high on a game? If they tell me I get bonus points for stealing their shovel, why wouldn't I choose that option? Nothing is at stake.
Also, the real world is rarely so symmetric. Most of the time, one party has diminished ability to retaliate, and so gets defected against much more often.
In a college classroom, where someone tells you you'll get fifty bucks if you score high on a game? If they tell me I get bonus points for stealing their shovel, why wouldn't I choose that option? Nothing is at stake.