The scheduling meetings are a jolly, always have been and always will be.
The IATA scheduling conferences are a different kettle of fish to Routes. Where else would you find "2,800 senior professionals who represent over 300 airlines and 750 airports as well as numerous governments, destinations and tour operators" under one roof?? CEO's, Vice Presidents, Senior Government officials?? Certainly not at the IATA scheduling conference.
I would suggest that if your airport is NOT at Routes, they will miss a massive opportunity to renew old contacts and make new ones. The fact that Vueling's interest stems from initial contacts at Routes some years ago is evidence that it does work. For the cost to the Marketing Budget of one trip to Routes, you can save a lot rather than if you had to make a number of speculative individual trips to see potential airlines.
And of course if you don't go, airlines will wonder why not and may take it that the airport is not interested in route development. Remember that the airlines are presented with many more proposals than they are able - or want - to take up at these conferences, but will follow up the most interesting in private after the short formal meetings, which is how the system works.
Don't expect instant results, but Routes is one of the best ways to get your ideas out into the market place at value for money cost.
On the other hand the IATA Scheduling conference is mostly about slots at slot controlled airports, with some airports being there to meet airline schedulers mostly.
Cardiff Airport needs passengers not Politicians, Planners or Pen Pushers
I'm sure many other airports share your sentiments. Unfortunately, the real world has these people who need to be brought into the loop. Airports need to inform and influence these people about a range of topics (APD for instance), otherwise they can cause a lot of damage to businesses.
Suzeman