[WhitneyLand]

What are the primary reasons people don't hurt each other more?

1) Unfavorable risk/reward ratio (threat of punishment or nothing to gain)

2) They are not a sociopath

You don't mind losing half the safety net right up front?

[tbrownaw]

I'm pretty sure there have been cases where laws were needed to counteract social pressures that pushed towards violence. Such as the origins of "an eye for an eye". Your item (2) seems to assume that social pressures are universally positive, or at least towards non-violence.

[WhitneyLand]

Not social pressures, rather having a conscious. The existence of empathy, compassion, etc has certainly helped the cause of mercy.

[tbrownaw]

Your conscience will be vastly different depending on what culture you trained it in.