Japanese are obsessed with being clean. Like wiping the pen with tissue paper before handing it to you. On more than one occasion I have had a stranger passenger on long distance train clearing my cup of coffee as she goes to throw hers in the trash. May be she is signalling you can't trust these foreigners to clean up before they leave!
I don't know about clean, I saw hardly any (men) wash their hands after using the bathroom. Sometimes they'd wave their hands under the tap. Without turning it on.
Seemed more like obsession with being tidy than hygeinic.
