I grew up in the country... my parents were not sophisticated city folk, so we were taught to bathe a couple times a week and wash yer hands if they were dirty. S'bout it. Didn't know what dental floss was until I was a teenager.
Now, as I grew older I started taking social cues from my peers and catchin' on to what was appropriate behaviour. However, I didn't wash my hands after urinating until I was in my 20s. And I was never sick. Healthy as a horse. I actually believe in the George Carlin's hand-washing theory, however, I wash my hands each and every time now so as to not offend peers.
I remember the old Leno joke:
"A new suvey released today says that 50% of people do not wash their hands after using the bathroom. They have a name for these people. They are called 'men'."