Because I believe that a cat shouldn't be restricted from the joys of nature, just my personal opinion. Yes, there are dangers out there, but there is for every critter, and many of them survive, and we can't keep them all in. The only reason she has even begun to be an indoor cat is because she is white and too easy to see at night. We have 35 cats and the only cat fights we ever get are between Toms and at breeding season, but those are only at nights, don't ask me why.
And I mean, by going outside ourselves, we are putting ourselves at risk for an unending list of fatal diseases, we could get shot or kidnapped or seriously injured, but we can go outside can't we? (Not trying to be harsh, not
at all, just saying..) Plus, there are no "leg traps" or coyote traps as we call them, out here because my dad manages this ranch and we currently have no traps out ourselves, and no government traps within many miles of the house. The two yard dogs do not terrorize the cats, in fact, the cats often rub against them and they do not respond. The only cat terrorizing dog we have is penned up and only let out under supervision, and the cats steer clear of the yard they are in when they are out.
We have lots of cats and they are all in risk for many things, but they all do great. The only time we ever have a cat die is from either old age or a coyote/owl got it, and this always happens at nighttime, when Zoe is in the house. We never get any cats from town or anything, we live 35 miles from town and 3 miles from the highway. I keep track of all of our cats, we never get any new ones except for kittens. I assure you, it is much safer for her out on the ranch than it is for a partially-outdoor cat in town. And she won't stray far, I assure you. She gets fed well here. But I think she should be let outside to play with other cats. I am lucky I get to keep her indoor as much I do, cause Mom didn't want an indoor cat, but she took pity on the poor thing, didn't want anything to eat her. But I don't really see the point in clipping her nails, as she will be under semi-supervision in the house so she can't tear anything up, she'll have a scratching post and mat, and she doesn't claw us except for in play and then it doesn't even hurt. But as I said, I am messing with her ears, teeth, and claws now so she is used to it.... (Wow, sorry for the long response, just wanted to give you plenty of resons to back up my opinion.

I hope you understand...)