In response to the OP rather than the absurd statistical claim made earlier
, in my admittedly limited experience, many cats who live in a terrace and aren't let out the front rarely bother to go round the front unless they have to, if there are pleasant places out the back for them. My first cat as an adult was mine as a student in a university town. We lived in the middle of a terrace and she went out the back and enjoyed our little garden and those of the neighbours. She hardly ever made it over all the fences and walls of 6 or so houses and back round the front, apart from one time when she was quite young and got lost - and ended up on our front doorstep crying pathetically. We were crying pathetically too as we thought she was lost forever (it had been 3 hours ...) and were watching The Aristocats to cheer ourselves up. It didn't work. 
She was great though - at the back of our garden, over the wall, was the local pub garden. We'd go round by the pavement and she'd pop over the wall when she heard us, and we'd sit together in the beer garden. Happy days.
Then I sloughed off student life and moved in with my bf in a house in the 'country' (edge of a village, after Reading it was the countryside to me!). She TOTALLY recreated herself as a huntin', shootin' type and started bringing back baby rabbits.
She had the best life ever until she had a stroke, which (obviously) had nothing whatsoever to do with her normal, natural outdoor life.
Conversely, I have a good friend who last year got a kitten and they decided that he'd be an indoor cat. They live, like us, set back off a road at the edge of the village with a huge garden and then fields backing, and they enjoy having their patio doors open all summer long. I have to admit I was sceptical - but he is now so unused to going out that he doesn't really try much, and I'm actually worried that when he inevitably does sneak out unsupervised, he'll come a cropper because he hasn't been able to develop any road sense. He is also obese, which for a cat of his age is tragic and actually makes me quite cross. They're trying to restrict his food intake a bit but I just want to scream 'oh FFS just let him out and run it off!'
I agree with a PP who suggested that rescues in the UK are adopting more and more American ideas about cat safety, but I also think this society is becoming a lot more risk adverse generally, and this is just one example. Cats need to roam - most want to - and unless you're living somewhere very unsuitable for that, you should let them if you want your cat to live a fulfilled, happy life. Rescue centres will have to accept that if they continue to be so unreasonable and picky, we will continue to go to commercial sites for our cats. I'm currently into my second month of actively searching - combing all the rescue centres in this county and a few others. I rarely even get a response saying no.
I don't know where all the rescue centres that are snowed under are, but not round here, apparently. I really don't want to go to a commercial site but I think we're going to have to.