I have both indoor/outdoor and outdoor cats. The indoor ones were all rescued as kittens from alleys, and so never developed a taste for the independant life. They are definitely very curious as to the comings and goings of the others, and make frequent escape attempts. My out/ in cats were rescued in full adulthood, some after having lived on their own for YEARS. They would just never tolerate being imprisoned. Every morning they are all climbing the walls to get out of here and check out their turf.
Personally I think it is cruel to expect an animal to be truely content in a house all the time. ( I would go insane being stuck inside myself, and I am a human).
But we expect all kinds of things from pets which go completely against their natures- That is what they were invented for: to be controlled and have their natures taken away for our entertainment. Very sad really. Really it seems to me that all pets should be spayed and neutered so that the entity ceases to exist.