Interesting comment that They can differ all they want but I have evidence to prove I'm right. I'm pretty sure others would have their own evidence to prove they are right too.. Sometimes one has to weigh evidence that may suggest both sides may have some validity, which you did state by mentioning not all cats would take to it. I'm mixed about it, can see advantages of both sides, which is preferable I do not know but as I don't have a cat living with me I do not have to make that decision.
People can think they're right, but they may be affected by bias, or just not understand the evidence perhaps, which can throw them off. Did you read my post on Feline Forums that I linked to about the many dangers of letting a cat go out? It's very informative, especially the infographic that I've based it on.
I wonder if a person born blind misses the benefit of eyesight, can you miss what you've never had? That too is open to interpretation as a person born disabled can miss being able bodied as they can see the difference.
The short answer is yes, the most definitely can miss what they never had, in many, or most cases. I'd say where they wouldn't miss it is if they have some mental impairment where they remain baby-like and non-verbal their whole lives, living in blissful ignorance of their situation. In this case, their simple needs are met by their long-suffering parents. I used to know someone like this and it was such a sad thing to see and the strain on the parents was obvious.
Animals born into captivity know no better but they look out of windows, GF's cat in California is not allowed out, hawks and coyotes are a danger but it gets so excited when it sees birds, squirrels and rabbits outside the glass doors. Are we so adverse to danger nowadays that we give up the excitement of sensible danger. Could go off topic here so shall leave it at that.
Those animals are likely to be blissfully unaware as long as all their basic needs are met. For big cats for example, large fenced parks are enough to make them feel free and happy, leaving them clueless about their confinement.
The cat that I know, isn't even especially curious when the back door is open and he can smell the outside. Sure, if the door was just left open, he'd eventually be curious enough to step outside, but he's always locked away or held in arms when that door is open so it won't happen. Hence, this is an example of a cat that's perfectly happy with its confinement, not realising what it's missing. Since he's only got one eye and hence disabled, it's especially important to keep him indoors for his own safety. I doubt he could catch anything.
Oh, don't worry about being off topic at NZ.
As I've explained in the rules, it's the natural way that conversations ebb and flow, so I don't want to stifle it. Where it matters, I'll make adjustments, like all those Trump posts that I moved from one thread to the other yesterday, or gently steer people back to the subject.
The most useless guard dog on earth. No treats for you today! 
