Could also be down to pure statistics. More people, more airfields darn sarf. There's not much north from here in terms of GA until you get to Scotland where it seems to pick up again. If I flew north from where I am I would pass reasonably close to Sherburn, Breighton, Beverley and than nothing until Eshott. Then nothing again until Dundee. If I fly south there are more airfields than you can shake a stick at.
Of course there are other strips but I'm talking about places where you could a least get a bacon butty and a cuppa.
Edit: Forgot Full Sutton and Bagby in my northwards trek before I get my head nailed to the ground.