It's ideally placed (about halfway up) to provide refuels for aircraft routing up and down the length of the country
Aircraft, much the same as commercial road vehicles, stop for fuel where the price is right without diversifying to far off their optimum route.
I don't know the price of fuel at a Sheffield City Air/Heliport but I would suggest that it would be more expensive that at some competitor airfields where those aircraft could stop for their refuels.