50 YEARS OLD OR 44 YEARS OLD?

Sabah, Sarawak and Singapore did not join Malaya but they merged with Malaya to form Malaysia on 16th September 1963. If that's the case, why are we celebrating 31st August 1957? Is it because Malaya's independence day is more crucial and important to be celebrated and not Malaysia's independence day? I see this celebration every year as an insult to Sabah and Sarawak. It is like you are part of the family but your birthday is never being celebrated. Then, what meanings do you have joining a family which ignores your birth date?