I believe that cats have traditionally been "mousers", killing rodents and
other small animals that poeple considered pests. Even today, it's not at
all unusual to find "barn cats" out in the countryside, who primarily eat
mice and snakes. The farmer (or rancher, etc) continues to rely on these
animals to keep the barns and silos free from mice that could ruin stored
crops and spread disease, and to keep the barns free from snakes that spook
the cows, horses, etc.

My Grandmother has an approximately 17 year old cat (Fat Cat) that turned up
as a stray 16 years ago when she lived out in the country, and it was always
a "barn cat", but it did get table scraps as a supplement, and fresh water.
Grandma moved to a small town to be closer to the doctor's office 4 years
ago, and she took the cat with her. Fat Cat now lives in the storage shed in
the back yard, with her own kitty door entrance, a straw bed, and heat lamp.
She eats moistened cat kibble (has a difficult time with hard food in her
old age) and comes onto the patio every afternoon to sunbathe and get her
tummy rubbed. She never leaves the back yard... All in all, sounds like
she's had a pretty good kitty life.