Everyone in Korea wears a mask. If you’re wearing a mask and have the virus, it’s harder to pass on to other people which works well when everyone wears a mask. There would be no point in wearing one in countries where people are so reluctant to wear them because it needs to be a large % to be somewhat effective.
Contrarily, barely anyone washes their hands properly here. Even in the midst of the outbreak, when I go to a public toilet, people (with masks on) would just walk out without washing their hands. Some would stop to style their hair in the mirror and then proceed to walk out. Some toilets don’t even have warm water or soap.