It's not different from nature. Neither are predation, parasites and diseases.

Stationary single point food sources would be rare but if there was one, resource guarding and physical competition would be normal as well, as would behaviours such as marking territory with urine.

Data from the US (where they have predators like coyotes) always give cats in the wild a 2-5 year lifespan.

I think the figures are better here, but cats in their natural state still have much harder lives than most pet cats.

Personally, if I have a pet my aim is to give it a long happy life, but I know mileage varies and everyone draws the line wherever they feel comfortable. I've mostly been lucky enough to have windows I can leave open for cats during the day.