One of the reasons for the 'fascination' with transatlantic services is the poor state of ground transportation in Ireland. In areas of the UK that don't have transatlantic services, there is a good chance that it's possible to get a direct train into Manchester, Birmingham or Gatwick Airport.
Consider the slog of getting to Shannon. No trains. A bus which takes 2 1/2 hours. No wonder connecting in DUB, LHR or AMS is a more attractive proposition. A direct flight from Cork is better again.
However, I can see the point that it's not the best next step in the airports development. As much as new routes, I'd like to see greater frequency on existing ones - Amsterdam and Manchester returning to 2x daily, Paris going to 2x daily, all the UK routes with a frequency lower than 1x daily going to daily. As regards new routes, Frankfurt would be as important as a US route.
Mind you, if a US route turns up, I won't be complaining.