Perhaps in part due to the reasons I like it that I mentioned above - on people's first (or second) visit, most are going primarily the smoke and mirrors experience more than anything else - everyone loves the magic after all
But there's only so much of that you can take before you start to want to diversify into some other things.
I think there's a bit of a Ying and Yang thing going on. At the beginning when we're on our 'once in a lifetime' trip (yeah right

) it's ALL about the Ying, baby
When it then turns into a long haul investment of years of holidays then people usually realise they need some Yang in their lives too, and for many I think that's where Epcot starts to come through more.