I have two indoor cats...one is 19 and the other is 12. When we take one of them on our back deck (with me right by her side) thinking she might enjoy the sun, she sits there for a minute or two and then cries to get back in.
They have never had an urge to go outside...and I'm thankful for that.
I live in the city and I can't even imagine letting my cats roam outdoors here. At the clinic, I have seen too many horrific things over the years as a result of hit by cars, poison, infection, maggot infestations etc. I would elaborate, but I would rather spare you all the upsetting details....
Yes we could easliy be hit by a car and no we shouldn't stop going outside. But we have to go outside in order to live and function in the world. We also know where to cross the street, and what a red and green light means (granted humans are still killed and/or injured by automobiles etc...but those things still work in our favour...you get the point). If a cat doesn't know the difference, why raise the chances of something awful happening by letting them outdoors?
I really can't comment about letting cats outside if one lives outside of the city as I don't know what the wildlife, shootings, etc. is like there. It would have to be pretty darn safe in order for me to do it myself anyway though.
Also, I think once you have had a cat that used to be outdoors in some shape or form it's a lot harder to keep them inside a lot of the time. I can totally understand why those in that situation would want to let their cats out.
I think my cats have a great life; therefore, I don't feel it's even an ounce cruel to keep them indoors.
In the end, I think everyone is just trying to do what they think is best for their animals.
Great topic by the way!