|DCA's World of Color|
Or it's because Disneyland is better, at least as a concise Disney park. I've always held this theory, but numbers don't lie, and they say that I'm right.
Other speculation is that WDW attendance is being siphoned off by the new Wizarding World of Harry Potter section at Universal's Islands of Adventure. This is probably also true. If it is, it wont last for long. Disney World will eventually open something that far outshines the wannabe Fantasyland "world" at the Universal park.
But look at the statistics on how the opening of the Wizarding World at Universal and the opening of "World of Color" at DCA. According to the OC Register's article, "Universal Orlando’s attendance jumped 36 percent since the opening of the Harry Potter-themed attractions in June" while according to Bob Iger, President of Disney, "California Adventure had a 20-percent leap in attendance since the debut of the “World of Color” show in June."
"World of Color" is a integral part of the DCA update happening in California, but it's not the main feature. Over at Universal, "Harry Potter" is their big shebang, their E-ticket attraction. It's the big thing getting people to walk through their gates. But it only raised Universal's attendance 16 percent more than a nightly water show, that can only be experienced twice in a single day for about 40 minutes total. I think that says a lot about the attractiveness of the things Disney does and thow Universal does things.
"Harry Potter" world will always attract people, but it will never be comparable to anything Disney does. Attendance will even out, and WDW will reign supreme once again. With the rumors of an Australia section coming to Wild Animal Kingdom or a reproduction of DCA's soon to be opened Cars Land at Hollywood Studios, Universal's Islands of Adventure will once again be a footnote to WDW in Orlando.