Consider: What normal person would consider risking their career and their family life in order to undergo the incessant barrage of intrusive questioning about every aspect of their lives since well before college? To face the constant pettifogging and chatter of Facebook and Twitter and have to boast of how many false friends they had made in a weird cyberland? And if only that was the least of it. Then comes the treadmill of fundraising and the unending tyranny of the opinion polls, which many media systems now use as a substitute for news and as a means of creating stories rather than reporting them. And, even if it "works," most of your time in Washington would be spent raising the dough to hang on to your job. No wonder that the best lack all conviction.
Who on earth wants to go through all that? Campaign finance reform would help, but a complete change in political and media culture is necessary before a halfway normal person would consider running for office. Until then, we'll continue to get the oblivious narcissists with massive egos that run for office now.