Basic Instructions

This just got installed above the sink by my desk here at work. It's a sanitizer dispenser. Simple enough, and it even comes with instructions on how to use it written on the front. Since the pic from my cell phone is sorta blurry, I'll type them out here.

• ensure hands are clean and dry
• apply 1-2 shots of foam
• rub into hands until dry

Now this is all well and good, but the question  I really have is this:
The first step is to 'ensure hands are clean and dry', now if my hands are clean and dry, why do I need the sanitizer?

Ponder.