Have you actually ordered from hatcheries, or tried to? Because what you're saying does not match what I've observed.
I can go to the website for quite a few hatcheries, and order chicks now, to be shipped at a time of my choosing in the next several months. That means I CAN order chicks from eggs that are not even laid yet, and the hatchery will set the eggs at the right time to hatch those chicks for me.
I usually find that chicks for the nearest hatch date (already in the incubator) are "sold out," or very few are available. (Exception: there may be sales on a few breeds that had a better-than-average rate of development during incubation.)
In order to fill all the orders, they have to hatch a few extra chicks of each breed (in case a few don't hatch, or in case the balance of male/female is a bit off.) But the hatcheries sell the extra chicks too, usually by grouping them into "assortments."
Even if it is "all about greed," they would not hatch a "huge excess" of chicks, because that is expensive. They have to pay for the eggs, pay to have bigger incubators, pay for the power to run the incubators, pay for people to tend the incubators, and pay for people to take the chicks out of the incubators (to box them for sale or to dispose of them.) All of those costs are a complete LOSS to the company if the chicks are not sold. So purely from a profit motive, they are motivated to sell as many as possible of the chicks they hatch, while disposing of the smallest possible number.