If nobody votes, what happens?
Have to buy a product? Since when was anyone in America forced to buy a product, or forced to vote?
I mean, that is a functionally impossible question. If everyone who disliked both candidates chose not to vote, you would still have tens of millions of voters.
As previously stated, if you don't vote, you aren't getting no president and a redo, you are just letting a bunch of idiots make the decision for you. And again, you aren't forced to vote, but you are forced to have a president.
Maybe the reason you aren't understanding this is that someone keeps making bad comparisons instead of just looking at the question at face value and seeing how simple it is. Like, we don't need abstract maths to do simple addition...