Because
(a Obscenely expensive. I can think of trillions of other vacation options I'd rather spend my money on.

(b I don't want to wait in line for 3+ hours to ride a 2 minute ride aimed at small children.

c) If I'm taking my children to a theme park (theme parks are for kids, imo), there are cheaper options, with less wait (very important if wanting to have a good time with small children) and rides that are just as good (Legoland is awesome, zero line, same with Universal Studios).

I now await my 7 day ban for speaking pure and utter blasphemy on Cougarboard.