For me personally, going to WDW is cheaper than going to any other parks around the world.
Beyond that, when I'm getting on a plane to fly to another country, going to a Disney park is not very high on my list of things to do. I'd like to go to DLP, but despite having already been to Paris once, whenever I go back there are too many other things I didn't get to do on that first trip that interest me more than visiting a Disney park. And although Tokyo Disney looks incredible, if I'm visiting Japan, I don't think I'd have time to visit a Disney park over many other things considering it'd likely be a one time trip.
Of course, I also don't go to WDW yearly (or multiple times a year) like some people do. It's certainly not what it was 25-30 years ago.