I won't talk as a breeder, because it's obvious that, if you breed for showing, you have to hatch chicks. So, I'll talk as if I had a flock not for showing-breeding purposes.
First. I like to know all my birds from the moment they hatch, so they aren't scared by me and it's easier not only petting them, but also picking them up for checking them, medications and medicines.
Second. Here you can't just buy chicks online from hatcheries or in a TSC-type shop, neither people sells day-old chicks on Craigslist-type sites. There are few farms that sell chicks, but they are all Cornish Crosses. Some feed-shops have one day during the spring where they gift you chicks if you buy feed-bags, but many people say they give you only or mostly males.

So, the only other way to have day-old chicks is to hatch them yourself.
Third. I hate quarantining. I sometimes buy grown birds, but quarantining them in a separate area of the yard it's always stressful for me because I keep these birds closer to the neighbours house, so I'm afraid to annoy them with them. Plus, the red-sexlinks (all the others never escape), like to escape so I'm always afraid that one will escape, go near the quarantined birds and then return in the flock. One time I surprised one near the quarantining zone,

she has passed the remaining time of the quarantine with her new friends. Luckly nobody was ill, so everything went well. So, returning to chicks. If I hatch them my own they'll have to stay in a brooder separated by the flock anyways, so it's like a quarantine, but without the risks of chicken escaping and going near the quarantine zone because the chicks are kept indoor.
Fourth. I know the whole clinical picture of all my chickens, with all the vaccinations they had and when and whose illnesses they were exposed to.
Fifth. I'm hatch and chick obsessed. I can't keep the incubator closed for more than few months.
