Sadly public transport is far to expensive for many people to afford. For me to get the train from Nottingham to hathersage cost close to £70 and takes nearly 4 hours each way. The car is an hour and about £ 10 in fuel.
Really? The actual train bit of that seems to be ~1:45 each way (via Sheffield) and <20 pounds for an off peak return.
Depends where you're able/choose to live to a fair extent of course. Sheffield/Manchester are great, Leeds/Bradford not at all bad. Also of course a huge help if you've got a really good, early morning/late evening, connection to/from the main train and bus stations.
The options for long linear walks is one of the really nice aspects. Also being able to flatten yourself a bit - having to drive back after some of the walks I do would be getting on for plain unsafe.