Why? I'll bet your grandmother or great grandmother looked forward to the day when one of the hens stopped laying. The old term is "stewing chicken". You couldn't fry it- it was so tough one couldn't cut the gravy. But for soup, chicken and dumplings, etc. it had great flavor. One of my last memories of my great grandmother was of her dressing out her last laying hen (too old to have them anymore) and making chicken and home-made noodles.
In her day, fryers were a once or twice a year luxury.