I haven't seen any evidence to suggest that the percentage of people wearing masks while doing anything other than taking public transit or walking on city streets was higher in Korea, Japan, or Taiwan than it was in China before the COVID-19 outbreak.
Wearing masks is not a bad idea, but it is not what was primarily responsible for the success Taiwan, South Korea, and Japan initially had in fighting the COVID-19 epidemic.
Based on my experience the number of people wearing masks in public pre-COVID-19 would have been slightly higher in Japan than China, but was still a small enough percentage of the population that it would not have made a significant difference in virus propagation.
True. What was primarily responsible for the success in Taiwan was catching cases at the airport and contact tracing of those infected. However, wearing masks AND hand sanitation ( they both have to go together ) probably had some effect. There have been slightly over 500 cases in Taiwan. The vast majotity of them are from people who were infected in other countries returning to Taiwan. The rest ( except one, a cab driver ) were people who were living in the same household as an infected person. There have been no cases of it spreading in the general public. Now having said that, those are for cases that people showed symptoms. I am sure there were probably people who caught it and showed no symptons ( mostly younger people ). As for the amount of people wearing masks pre-Wuhan and post -Wuhan. , I can only go from personal observation. I live in Taiwan. In the area I live ( south of Taipei ) , I would say about 10 percent of people were wearing masks ( it was flu season and that is about normal ) pre Wuhan. The day after the Wuhan news broke, it was about 75 percent were wearing masks ( it would have been higher, but there was a shortage ). Right now I would say it is about 90 percent. I think the main advantage of mask wearing is not in protecting youself from inhaling the virus ( they have to be worn properly for that, and some people don't wear them properly ) , it is to prevent contamination of surfaces where other people can pick it up. The main thing masks prevent is someone rubbing their runny nose with their hand or sneezing into their hand and then touching something.