Why would you play Diplomacy if you can play Twilight Imperium 3, A Game of Thrones the Board Game or War of the Ring instead?
Pretty sure us "alpha-nerds" would rather battle it out in fantasy/scifi settings than with boring old "real world" troops (Here I Stand is excellent if you want that). All of those games are also a lot better imo.
Always thought Diplomacy was pretty meh :)