For someone in Hawaii, it may be easy to forget just how tough upper midwest winters can be. It is best not to have wee chicks hatched in fall. Since daylight hours are constant in Hawaii, it may also be easier to forget the maturing pullets need sunlight. We really want our laying pullets to be hatched in late February through March. These pullets stand the best chance of coming into laying form before the deep darkness of the following winter. A summer hatched pullet has no chance of maturing until the following spring. That's a lot of feed and a long wait for eggs. Many of us have an agricultural or homestead aspect to all this.
Collecting fertile eggs and keeping them cool in the heat of summer is almost impossible. Shipping fertile eggs to customers in the heat of summer is risky business in hot Post Office trucks.
Finally, many breeders use rather small match systems. This isn't the old "one rooster to 10 hens" ratio you hear so much about here on BYC. With small number matings, the hens can be over mated and that's tough on the female. She needs a break. The cock birds also need time off.
Fred has some good points here.
I frequently keep a rooster with my production layers all the time... but never fewer than 10-15 (preferably more) hens because they just get worn out. And even then, the roos always have their favorites who always looked shabby... but those were also my best layers. Being a sustainable farm, when I am down to only 1 production roo (like right now) I like to keep one with the hens in case something unexpectedly happens and I find myself without a roo - at least I have fertile eggs and don't need to bring in new blood. But... this is just for my production layers... a self-perpetuating practical aspect for emergencies. Not to mention they can be handy at discouraging "minor" predation.
For heritage or rare breeds I just don't want to wear the hens out. Longevity is a higher priority than flash in the pan heavy and fast laying, easily replaceable hens.
I have raised Cornish x's several times and have found that fall is actually my favorite time of year to do that... scheduling them to arrive about Labor Day. The nights are beginning to cool down a bit, but I still have forage through Oct or Nov, but it's not so hot to prevent good growth. Unlike spring, things are pretty quiet here (as in lambing and calving are over), so fall is a quiet time of year with more time. Also, processing 50-100 meat birds in November is nice when the weather is cool.
As with all the males here though... you must play well with others when it's not breeding season or you can't stay. Bulls must get along, rams must cohabitate nicely after breeding season, etc. I do not provide individual bedrooms for bulls, rams, and roos. Play well with others or the slaughter knife is always handy.
My husband is glad he is the only human male on the farm.