sure a lot of people do that.
it's closer to what the cat is naturally adapted to, and the cat will probably be a bit better psychologically adjusted in that case, but it's also a lot more dangerous for the cat, very often, depending on what the outdoors is like around where you live
the out of doors also contains things like fleas and other parasites that you might want to think about
i always kept mine inside. they generally live longer that way, and if you give them a lot of attention (and preferably keep 2 cats together that way. or what the hell, 3 cats), they won't go totally nuts.