Because MK has significantly less rides than its Disneyland counterpart, so you have massive queues for rides like Winnie The Pooh, Peter Pan & Seven Dwarfs Mine Train. The park needs significant capacity since it being the number 1 park cannot change. When TRON opens, there won't even been an E-ticket added in 27 years!!!! In fact, 20K Leagues Under The Sea was removed so we are in a deficit. That is a massive problem. MK needs expansion as do the other parks for capacity. But what they are doing currently is they are adding IPs that can draw people into the other parks. TRON as a ride will, but not too many people love TRON the IP.