Great pictures, and Merry Christmas!
My parents are both from HK, so I have some cultural theories regarding HKDL's Main Street and castle...though I really do wish that a bigger castle was made! Please don't be offended...I'm speaking from experience and in general terms!
Change. The Chinese populations in CA are VERY high, especially when compared to FL, Paris, and Japan. So HK people tend to not have been exposed to the larger castles. The Chinese culture is all about OLD traditions and therefore lack of change, and they tend to be stubborn about it.
Money. Frankly, Chinese people are cheap! (The park is owned mostly by the HK government)
Extravagance. HK people are minimalistic. Everything is in small portions, there is no Costco, and even taking food home from a restaurant is seen as shameful. A large castle may have very well given the park a negative image, especially when it's the people's money at work!