It's all about mitigating risk.  A drop on the lips, maybe you use your teeth to pull off wet paddling gloves, vs. a gallon to drink.  Somewhere in-between lies the reasonable precaution.

Since we seem to have gone from just the water risk to the overall concern of these bugs, toilet practices too.  I didn't use to worry.  Then I learned.  Now the only time I'll use hand-sanitizer (Purell) is on a camping trip.  The little bottle fits perfectly in the tp tube.  Especially for group trips.