They don't want their citizen to be corrupted by vice's.. In a sense they want to create a greater society, but there is too much corruption taking place for any immediate change. I think it will probably take around 25-50 yrs to phase out the corrupt officals.
Macau is a SAR. They had casino before the return of ownership to China. =P China is not trying to interfere too much with Macau,and Hong Kong, because they want to avoid conflict with Taiwan. By not interfering, they want to show Taiwan will be free if they return to Chinese rule.