Because we live in coyote/car "country"...our cats are indoor only, with the exception of Livvy, "indoor in her enclosure".

Its just too unsafe where I live. We are constantly hearing, "Oh, we don't have "kitty" anymore, she was coyote bait (instant embaressed smile after I glare at them), this is our new cat". Nice...

When we have a house, I'll let them out one at a time so I can watch them play. I know most of them would LOVE rolling around in the grass.