Have you washed your hands?

You wash your hands when you come back home. Some of you even gurgle.
I asked a few foreigners, from time to time, if they wash their hands when coming back home. For most of them, the answer was "no". Then are they more susceptible to diseases caused by viruses or microbes? I have no statistics but I suppose it is not likely. So washing hands on coming back home is rather a question of culture and may not stand on any scientific ground.
The other day, when I read a novel written by an Indian writer living in Canada, there was a scene where a mother tells her kids to wash their hands whenever come back home. There was another scene she tells them to change their rain-wet clothes for fear of getting cold in spite of the fact that Mumbai is a very warm place. These customs could have traveled to Japan long time ago by some chance from a hot place in Asia where germs are having a field day.
A British guy once said when I pointed out their bad behavior of not washing hands,
"It is good to intake microbes around us into our body so that it can create antibody and make it ready to fight with them."
He has a point there.
It is interesting to know how we are used to our behavior without giving it any thought. Superstition and science are only separated by a very thin line.