I think you are on-target here. Dunno what got into the philosophical mainstream. The contract ideas are profoundly at odds with how social creatures (including us) work in practice--and it's not like these things couldn't be observed easily enough.

Enlightenment thinking and values are broad enough to handle this in stride, but it torpedos the kind of argument Jarvis-Thomson makes: as a social creature, in fact, you do end up with all sorts of responsibilities without explicit commitment.