I don't know I guess its habit. Many machines do not have fast revolving
brushes.
I often have thoughts about muck. where does it all come from?
Not all of it can be shed skin, so one must assume its come from outside
and maybe even outer space.
Brian

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"DerbyBorn" wrote in message
2.236...
Why do we scrub the heavy thing back and forth when it has fast revolving
brushes? Surely a single slow pass is just as effective.