It's almost certainly about being a nuisance to your neighbors. Roosters crow super obnoxiously. Like.. wow. If you've ever tried to sleep with one nearby you know what I'm talking about. Just handle that edge case (e.g. don't keep a rooster around) and NO ONE will care if you have chickens that don't bother anyone :) Especially if you're into sharing the eggs!
Commercial chicken hatching operations separate chickens by sex and destroy the males, yes. Backyard operations rarely hatch their own chicks but rather buy them from suppliers (who deliver via USPS, surprisingly enough).
You only need one rooster to ten-fourteen chickens anyway, but they are 50% of the chicks, you do the math.
Anyway most don't hatch their own chickens, because without a machine you will have trouble finding a hen that can do it - but I assume this is a western thing, as it is a fairly recent development (ie 100 years ago it would have been no trouble).
