If we can get past the personal sniping for a minute. . .
The social contract is different from a legal contract that you must sign in order to be bound by it - as different as is a contract in the card game of Bridge.
The social contract conforms to the first dictionary definition below:
1. an agreement between two or more parties for the doing or not doing of something specified.
Social contract is a group of patriots deciding that their government would not dictate, reward or endorse religion while at the same time the government would not interfere with the people's religious beliefs or expression of their religious faith in any way.
Social contract is a group of farmers, ranchers, and business people getting together to form a volunteer fire department that would benefit all.
Social contract is a developing community agreeing to organize a mutual water district instead of everybody operating their own wells.
Social contract is a developing community deciding it isn't practical for everybody to supervise the fire department or law enforcement officer or water district and choosing a mayor to oversee those functions on their behalf.
In every case it was the people deciding what their society would be instead of the government dictating that to them.
Others who would come along would not be party to those decisions forming the contract, but would nevertheless be beneficiary of them.