I don't want to belabor the obvious, but I wonder if anyone has considered that perhaps young, urban ethnics (whoever the hell they are) just don't care about nature walks?
Actually it is not really even a matter of urban or race. Young people are like me at their age out trying to interact with other young people. That means bars or other such activities not national parks for most young people.
The Labour Government can huff and puff all they want, but I suspect young men and young women will still be trying to get together and I doubt the moors are a good place for that for most people.