Why handwashing takes more than a quick rinse
Hands are not smooth surfaces. Microbes and dirt can sit in skin creases and around fingernails, where a splash of water may not reach them well. Soap helps by loosening oily grime and particles from the skin; rubbing then moves them into the wash water, which can carry them down the drain.
Time gives your hands a chance to make contact
The useful work happens across the whole hand, not just the palms. As you scrub, spread the lather over the backs of your hands, between your fingers, around your thumbs, and near your nails. Those spots are easy to skip when you are rushing, even though they are part of the surface that needs cleaning.
A familiar song is useful because it gives you a steady, repeatable measure. It is not a disinfecting incantation: the point is to keep washing long enough to cover your hands thoroughly. If you stop as soon as the palms feel clean, the untouched creases and fingertips may still have what the rinse was meant to remove.
The rinse completes the job
After scrubbing, rinse away the loosened residue rather than wiping it onto a towel or clothing. The sequence matters: soap helps release material, friction helps dislodge it, and rinsing removes it. The song is simply a memorable way to pace that sequence while your attention stays on the places your hands tend to miss.
