Joseph Ellis addresses this question in Chapter Four of Founding Brothers. Essentially, he suggests that Washington embodied a fundamental dilemma of postrevolutionary American politics. The new country needed a powerful leader that could focus the "energies of the national government in on 'singular character'" with the prestige to hold the government together. In tension with this reality was the "inveterate suspicion of any consolidated version of political authority" that had been a legacy of the Revolution. As Ellis puts it, "what was politically necessary for the survival of the infant nation was ideologically at odds with what it stood for." Ellis interprets many of Washington's actions, from his public appearances that were carefully crafted for effect to his decision to step aside after two terms, in light of this paradox. Washington was constantly having to walk a difficult line, and he, unlike other presidents, had no precedent to follow.
Source: Joseph Ellis, Founding Brothers: The Revolutionary Generation (New York: Vintage Books, 2002), 127-128.