In one year in the 1920's there were only 15 public poetry readings in the whole of the US and 12 of them were by Robert Frost! I would say today that they would number in the tens of thousands. In the 1920's and before that the reading of poetry meant just that - you read the written poem but performance was not expected. Frost had a strong interest in sounds and sound poetry so he was willing to do live performances of his poetry.
In the last 10 years we have seen a tremendous democratization of poetry with a move away from the universities and into the libraries, coffee houses and bars with slam poetry and well attended meetings where poetry gains its voice.
This is a welcome trend and it has liberated poetry from formalism and placed it within the public eye (where it began and belongs).
Performance poetry continues the storytelling tradition of our earliest forbears who lived and declaimed in a pre-literate society.
Long live public poetry!