You are conflating 'clean' with 'sanitary'. You may have washed the dirt and oils off of your skin and hair but your body itself contains, produces, and provides habitats for all manner of organisms, cells, and biological and chemical substances that slough off onto anything around it. Take sterile cotton swab and rub it on your 'clean' post-shower butthole and grow a culture from it and tell me how 'clean' it really is.
