Go to China and the level of ambient noise is much higher, whether that is people talking louder or having no qualms playing music from their phone speakers at any time of the day.
So at a guess, I think that cultural conditions probably lend themselves to people of Asian heritage learning to sleep under noisier conditions. Of course, these are all anecdata and generalisations so ymmv - fwiw, my personal observations are somewhat in line with yours.
