It’s not just about touching the “pubic” area. It’s about touching any part of your body between, say, mid-thigh to mid-belly. That entire area is just covered with e.coli and other assortied nasties. (You’re soaking in it!) I get this information, of course, from Cecil’s column linked above, which should be mandatory reading for all schoolchildren.
Of course handwashing doesn’t kill 100% of everything (after all, the germs that live permanently on your mid-section don’t wash off when you take a shower) but it goes a long way towards thinning the population of what you just transfered from, say, your hips to your hands, just by the act of pulling your pants down.
I myself keep a mental list of all guys at work whom I have ever seen not washing their hands, and remember never to touch anything that belongs to them if I can avoid it. If I was a mean guy, I’d leave anonymous notes all over the office pointing the finger at the Unclean One. When I see a guy leave a stall after doing a groaning #2 (or any stall activity, for that matter) without even bothering to “pretend-wash” his hands if only for my benefit – well, let’s just say I have a pretty low opinion of that person thereafter.
Of course it’s because of these “pretend-washers” that you have to use paper towels, or your elbow, to turn off the taps after you wash your own hands. Think about it: guy smears himself with god-knows-what, guy operates the taps without using soap, guy rinses hands for exactly one second, guy operates taps again, guy dries hands on guy’s pants, guy opens door (inevitably a design where the bathroom door opens in, note, office architects*). There is now e.coli smeared all over all the surfaces I need to touch, after washing my own hands, just to turn the water off and get out of the bathroom. You better believe I’m gonna protect myself with a paper towel, ineffective as that probably is. At least I’m doing something with my hands besides wringing them.
*Bathroom doors in public places should open out, preferably with no mechanism to turn the latch, so you can just sort of lean out of the bathroom, shoulder-first. Either that, or post armed guards inside the bathroom trained in handwashing enforcement.