Regardless of the population of Yorkshire it simply wouldn't be able to make a "proper airport" work. The usual holiday destinations and cities yes but that is because airlines can make money from that type of destination with small to mid sized aircraft. The airlines have chosen Manchester to serve many more short/mid and long haul destinations because they know its the most accessible and will generate profit.
I think there are many on here that have no clue as to how airlines work and assume having a bit of tarmac equals the belief we deserve lots of flights.