Warning: the following document makes repeated use of the word "ass," as well as oblique references to various bodily functions. Readers under the age of 18, or those with frail sensibilities, should just buck up and take it like a man.
There are certain unpleasant physical realities that we've come to accept in our lives. Things we've learned to just endure with a willing cessation of thought on the matter. This is proof of the adaptability of mankind, and our willingness to endure physical danger, or at least unpleasantness, in trade for the social contract, and the safety of living in large groups.
Take, for example, public toilets. Every day, most of us use public commodes to take care of our personal waste disposal needs. And we do so, for the most part, without thinking about the hundreds, possibly even thousands, of asses that have sat bare on the seats of these devices before us. In my mind, this is similar to the voluntary delusional state that allows us to take advantage of the "Five Second Rule" for fallen snack foods. (In some cases, this is extended into the "Five Hour" or even "Five Day Rule," but generally only by those types who particularly necessitate self-delusional states in the rest of us. See below.) In both cases, a tolerance level is established which is higher than mere reason or common sense would dictate.
Overall, it's fortunate that we have the ability to overlook the facts of previous toilet seat usage, as it is almost assured, statistically, that at least one of those posteriors belonged to someone with dubious hygiene habits. Even if your particular favored facility is cleaned with the most assiduous care, there's almost always going to be at least a handful of bottoms between you and the last time the stall was "sanitized for your protection." It's unavoidable. Sure, one can wipe down the seat with toilet paper, especially if there are obvious unpleasant signs of previous occupancy. Let's be honest with ourselves, though. All this does is assure an even application of germs to one's buttocks. (Not that I would advocate the complete abandonment of this practice, as there are times when necessity dictates the use of commodes that challenge even the most hardened of psyches.) Most reputable establishments also provide some form of tissue paper seat protectors, or "ass gaskets," as they're known amongst custodial professionals. But, again, we're fooling ourselves. Has anyone ever done research to confirm the anti-bacterial properties of thin white tissue paper? Are there university studies out there somewhere that I have missed? I've seen many a movie where the Center for Disease Control is called out to contain a biological disaster. And never once have I heard, "We have a Level Four biological emergency! Repeat, Level FOUR! Break out the environmental isolation suits! And be sure to bring lots of white tissue paper!" Of course not! Why? Well, first off, they'd have a more official sounding name for it, like "Thin Film Wood Pulp Bacteriological Isolation and Containment Sheeting." And second, it'd just be silly. All those Sani-Gards™ do is provide a false sense of security to those of us still uncomfortable with the realities of day-to-day life. That, and provide an audible signal (in the form of crinkling noises and the inevitable sotto-voce swearing that accompanies installation) for other occupants of the restroom. They're a subtle alarm that announces, "This stall contains someone who isn't really comfortable with living around other humans yet."
This may be more of a concern in men's restrooms, though, considering the dual modes of toilet usage employed by the average male. I wouldn't know about women's restrooms. Since elementary school, those have been a mysterious Terra Incognito, at least for me. Once, during my formative years, I chanced to glance through an open women's room door. I saw a couch. A couch! This clearly proves that the female of the species has different requirements from their sanitary facilities than the male. However, due to certain biological and logistical realities, the mental leap required to forget the previous toilet users, in many instances, may be easier to make for women than men. This is because of the simple absence of visible residue (by and large) from the occasional sloppy user of said toilet seats. (Co-ed restrooms are a test of psychic stamina for both genders.) After all, if you'll forgive the basketball metaphor, women are essentially confined to "percentage shots," while men are encouraged, by anatomy, to vary their urine deposition techniques. I am convinced that some males attempt said shots from the three-point line, or even mid-court, given the assaults to my acceptance of human interactive reality with which I am sometimes forced to deal.
Regardless, I am willing to concede that a similar, or even higher, need for protective self-delusion may be required from women. I am fairly certain that this is the case in sporting arenas and similar venues, where there is generally a line to use said facilities. My guess is that women would be on their best behavior in such cases, however, while under the watchful eye of the following user. I simply do not have enough data to hazard a guess in the case of normal female restroom environments, aside from the expected near 100% Posterior Contact Per Use factor in women's restrooms. (I'll put aside the mysteries involved with "putting on one's face" and "freshening up" in my calculations. Given that all modern public restrooms are required by the Uniform Building Code to have GFI receptacles near the sinks, I would deduce that power tools are somehow involved.) Men's rooms, of course, have alternate facilities that do not require any direct physical contact during use (aside from optional obscurative leaning sometimes employed in crowded public restrooms). This reduces the PCPU factor considerably. But there is an altogether different set of problems associated with these devices (the so-called "curse of the tan trousers," for example), which are beyond the scope of this document.
By this point, gentle reader, I assume that you are wondering if there is a point to this lengthy and somewhat unpleasant diatribe. That, or you have left in order to research Indian levitation techniques, in order to avoid the problem altogether. The point, for those of you who haven't had their carefully tailored blind spots shattered to the point of seeking mystical solutions, is that there are prices we must pay for our participation in civilization. There are taxes, the oft-lauded desire for more elbow room, the occasional need to endure the musical tastes of one's neighbors, and so on. And, perhaps most important of all, there's the need to develop the ability to turn a blind eye and a deaf ear (not to mention an insensate buttock) towards the unpleasant truth that human beings are fundamentally disgusting creatures. Lacking this ability, we'd never be able to even approach another of our own species without cringing.
And, I expect, we'd spend considerably more time performing odd little dances while we work up the courage to use public toilet facilities.