During my MOE era, I had a French colleague who once expressed surprise that Singaporean teachers are not outspoken. He came from a climate where speaking up was a norm. He taught in a school in England where the teachers banded to rid of the principal.
I told him that because Singaporean teachers are well paid and do not want to rock the boat.
Personally, I do not believe that Singaporeans are inherently reserved. It is just that the system has generally worked well for us.
If the system becomes broken, you will find that people will be very outspoken.