[squidfood]

Well sure, "social contract" is an imperfect metaphor, but it's not devoid of meaning, nor divorced from the idea of contracts.

It's the living that bind the living.

Specifically, previous but still-living generations. No one comes of age in a vacuum. If you inherit the benefits (or situations) of the previous generations, you don't just inherit the good stuff, you inherit the debts of the previous generation as well.

Looking way, way back, one can say that the first settlers in a given region might have formed a consensual contract, and the "social" contract is what each continuous generation inherits.