Do the math. The ideal ratio in a mixed flock is 1:10-12 hens. Factor in the many flocks owners do not want any roosters, or may not be able to have them. So there are positions as pets or flock husbands for maybe 10% of all roosters, a good 90% or more are surplus.
It would be impractical, almost impossible, to keep every rooster you hatched unless you kept them each to their individual cage. And that would be an unpleasant existance for them.
I think that most roosters have their purpose on a plate somewhere, on the table of a home with an appreciative family or in the kennel of a fortunate animal. And really, there are a lot worse things that could happen to a rooster than to enjoy a pleasant life and be quickly & humanely dispatched, then go on to nourish others.