I guess they've researched and found that people (besides maybe the small minority of Disney "fanatics") will go out of their way to travel to other parks just for some of the "unique" attractions. So they cater to the "locals" for that park.
I mean .. we here are excited about Tron and Ratoutille because how many of us would travel to overseas to go to a Disney Park just because of those attractions? But now we are excited about "copy/paste" attractions .. because they are "new" to us .. and it is probably infinitely cheaper to reproduce an existing attraction than create a whole new one. I'll take more "new to us" attractions than less "totally unique" attractions.
And even though the "attractions may be identical, I am sure there would be enough differences that if you visited a copy/paste land (like SWGE in
Disneyland), it will be still exciting just because of some of the other differences in the parks as a whole.
The copy/paste between the two coasts is less thrilling, but the same logic applies. I would guess a small minority of Disney World goers would ever to go to Disneyland .. (cheaper to drive/fly and WDW just has more parks) and if so . .maybe a "once in a lifetime" trip rather than the regular trips that happen here on the East coast.