This is a concept that actually exists. Would probably be wise to read about it.
Isn't that the principle of authoritarianism?
Sure, you have vote, you may ot many not have freedoms depending of the country, but did that person accepted that social contract?
What is the difference with slavery? The social contract is basically slavery of born children to do whatever the "nation" says. This is not different than a slave and their owner.
The concept of social contract is descriptive. "Descriptive" as in it "describes" something. It has nothing - as in 0% - to do with forcing people to accept anything or authoritarianism.