Because they can! As long as they think they can get away with it, they will try spreading their wild oats, if only on Twitter and in cyberspace. This, of course, is deeply ingrained into the male psyche, DNA, and evolution has a lot to answer for.
There is an element of exhibitionism and sexual repression that men succumbed to in the olden days. In my childhood days, girls all knew a weirdo who had flashed his manhood at them. Now it seems to be a bit more private behind the screen of social networking. But who are they kidding? In the end they are all found out. IP addresses are reliable sources easily traced and pictures and videos don't lie. Cases vary depending on their level of celebrity. So does their need of confessing to something "bad" they did and that they "really feel sorry for." I only feel sorry for their poor wives who are cajoled, forced, cornered into collaborating and putting on a chiseled face standing next to their object of love, fame, and now embarrassment. And their public admission of guilt will make the gullible public pardon them and forget. Why? Because a lot of men have similar proclivities and sympathize with them.
Marriage vows bind us, but was that what lawmakers and bible-writers had in mind? The media circuit is ruthless and quite different to what anybody could possibly have envisioned. Most perpetrators don't seem to know when to hold it or rather tuck it away.
Rachel Maddow's Sex Scandal Chart is priceless in its graphic explanation. Her main criteria are "creepiness" of the offense and the "criminal, prosecutionable aspect". Many a name on that list had already been lost in the fog of obscurity like Vitter. The prime culprit who refused to step down and got away with it, became very popular again in spite of it, of course is Bill Clinton. So did Spitzer whose abuse of government's money with a real madam is the topic naughty novels are made of. Now he is rehabilitated and has his own TV show. Life can be stranger than fiction.
Other countries have their rakes in political circles as well, i.e. Berlusconi or Daniel Strauss Kahn. European politicians and private persons enjoy the freedom of being allowed a mistress or two, or one after another. No need to resign because of such a trivial matter if your culture accepts promiscuity. Did they think they enjoy immunity, or that maids and subordinates won't dare to speak the unmentionable? They probably never even gave it a second thought. A twitter photo of a rather uninspiring male chest appears rather lame to me in comparison. With his leave of absence, Wiener (which means a type of Austrian sausage btw), is skirting the issue for the moment. What happened is real a shame for an otherwise brilliant, outspoken political mind that the democratic party badly needs to rally the base. With hypocrites acting as sexual jerks on both sides of the big divide, at least this one didn't contradict himself in taunting family values.
An excellent article by Lynn Johnson in Opednews.com today reasons that moral education has been mostly abandoned in our secular post-modern world. "The idea of trying to inculcate morality into young children seems both quaint and tainted. For much of the twentieth century, sociologists tried to demonstrate that bad behavior was not the result of moral choice but rather because of social conditions. Poverty, it was argued, caused crime." Has it all been for naught or do less prominent men show more self-restraint? We all have our fair share of experiences with that unsavory topic. You judge for yourself.