And some have a clue and don't wear white anything.

Don't have white sheets or towels either.

You probably got used to the slight greyish film after a while (I did so
too, once). Even coloured stuff looks brighter and cleaner if washed again
at higher temperatures, at least occasionally. Then there are problematic
stains (like grease and sweat) that won't get removed completely at low
temperatures.

Same with greasy hands (after repairing a bike, e.g.) where some dirt won't
easily come off even with special soaps but will with warm water.

You probably do know that it's because of a physical law (Brownian motion)
that higher temperatures dissolve dirt more easily and much quicker.

In its medical literature, the Food and Drug Administration states that
hot water comfortable enough for washing hands is not hot enough to kill
bacteria.

Also:

So while many believe hot water is more effective for hand washing the
study actually concluded, "the temperature of water used is not related
to how well pathogens are eliminated during the process." Additionally,
warmer water can irritate the skin and can affect its protective layer,
which may cause it to be less resistant to bacteria.

http://info.debgroup.com/blog/bid/33...-washing-hands