Usually, fees such as the development are simply added on top of the other fees airlines collect as "fees and taxes" on behalf of third parties (although a fair amount of these taxes a) technically are not "taxes" and b) are stealth taxes pocketed by the airline rather than passed on).
With airlines being more and more forced to include these taxes and fees in the price they quote right from the beginning of the booking process and in ads - and with these fees escalating more and more, making travel more expensive -, they are obviously reluctant to collect any additional fees - such as the "development fee" - on behalf of the airport. Remember the drama with Ryanair and Knock and Kerry airport when they both introduced "development fees".
If the airline is unwilling to collect this fee, the airport's logical solution would be to simply raise handling and landing fees the airline has to pay. Not a smart move nowadays, with more and more regional airports being totally dependent on one or two low cost carriers - that usually threaten to stop services etc etc. whenever such an idea is entertained by the airport.
So the solution is to look for the weakest link, which is the passenger. Will he be seriously annoyed to be forced to pay the fees? Yes. Will he stop using the airprt because of that? 99% will moan and groan, but will keep on using the airport.
If you think the whole thing through, in theory you could have airlines offering just the tickert for a. say, 10 quid fare, and before you enter the plane, you will have to pay a fee separately to:
- the car park operator
- the airport authority for using its terminal
- the handling agent to check you in
- the security company to strip search you
- possibly another handling agent that is doing the airside work
- [add whatever additional ides you have]
.... and the whole set again on arrival at your destination.