Yes, and I wash my hands also. But consider that you don't often shake penises as a greeting. I presume the GP's theory to be that a penis doesn't need to be washed regularly because it seldom contacts foreign bacteria.

I don't urinate on my hands...

On the other hand you're touching dirty stuff (like keyboards, or doors in public places) with your hands much more often than with your penis.

One would hope.

Typically you touch less things with it :)