The problem is three-pronged: we aren't writing historical plays, we aren't finding imaginative ways to stage our classics, and we rarely go beyond costume drama when handling the classics of other cultures. In the 2008-09 season, there were 18 play revivals; 11 of these were staged by English directors and one (Exit the King) by an Australian, Neil Armfield. Clearly, when a producer wants to do Godot or Hedda, they assume only a Brit can understand the material properly.
It's ridiculous. We have directors with a sense of theatrical past. Well, one at least: Bartlett Sher. The head of Seattle's Intiman theatre seems to be the go-to guy for revivals produced by the Lincoln Centre theatre, New York's default outlet for heritage plays. Last year, Sher won the Tony for his glowing version of South Pacific. In 2006, he was nominated for his assured staging of Awake and Sing by Clifford Odets. And this year, Sher delivered a glorious version of the aforementioned Wilson drama. Can it be that he is the only director in America who knows how to revive older work? Ask a New York theatre insider to name someone else, and they'll be pausing for quite some time after dropping Sher's name.
RTWT. I would add that the ahistoricity of post-Reagan American Culture is also kind of an issue here.