When it comes to connection to local population NCL is right at the top of the list - so stop moaning!
The airport is badly served by the road network and yes the airport's intra West Yorks. position is not ideal this is exactly why the link road as an absolute bare minimum should be built- to avoid the obstacle course.
I believe MAN has had a slight dip during the last 5 or so years? Wasn't it up to 23 million around 2008? So basically ringwayman the fact that there was a choice of mode of arrival to MAN after the station was built made the airport all the more attractive to potential passengers. When booking holidays the fact that you can if you choose to use the train makes you book the flight from MAN. The same can be said about having a motorway to your front door. Man more than doubled its passenger throughput in 15 years ish. They did not all arrive by train but the government had encouraged them to somehow get to the airport. Go on 10 years and instead of more flights to Ibiza you now have flights to china. That's how having good connections helps airports and regions. Its not about how many people go through the train station its the money they spend in the shops and bars at the airport that create the jobs whose wages are then spent in Salford or stockport instead of headingley or ilkley. There is also the fact that there would be people who live near to LBIA who would use the rail link to get to Leeds quicker - I am not sure if many do that from MAN train station. It is incredibly difficult to calculate the monetary benefit of rail link to LBIA in terms of what it would do for the region in general.