The benefit to hatching your own eggs is that you can expand your flock without setting up a quarantine zone or worrying about transferring diseases to your current flock. Hatching eggs can be educational and save you money. Eggs hatched in an incubator are generally raised by humans and bond to their caregivers; this makes the birds friendlier. When hatching eggs, you're pretty likely to get a 50/50 mix of roosters and hens. This has its drawbacks, but sometimes store bought chicks tend to be majority roosters. I anticipate experienced chicken keepers often properly identify the females and purchase those when the chicks are first put "on the shelf," leaving the males for the layman who isn't as knowledgeable. If you buy the heavily discounted older chicks, you're likely to discover those chicks are all roosters.