Hatcheries mass produce birds. Their parent stock strains are often not up to the standards for the breed type, according the the Standard defined for each breed by the APA.
Hatcheries mass breed by having 300 roosters in a large pen with 2000 hens. The more eggs are laid, the more chicks are sold, which increases sales/profits for the hatchery. Many hatcheries produce hundreds of thousands of chicks or more each year. There is no mating up of individual rooster with specific hens in order to produce better birds, eliminate faults or to meet the Standard. Hatcheries provide a service by producing mostly healthy, cheap and abundant numbers of chicks. That's what they do best.
A breeder, a true breeder has stock that can produce birds that meet the standards to an extremely close degree. Matings are limited to only this or this cock bird with this or this hen to produce very fine birds. A good breeder can only produce a limited number of select birds each year. It is deliberately small in scale.
Finally, not everyone who "breeds" and sells egg and chicks are breeders. Lots of folks have rather ordinary stock and it might be better to call what they do propagation.
Hope that helps.