It's because the vast majority of the respondents are going on name recognition and vague impressions this far out. The cross tabs and all the other small details from presidential polls right now are close to meaningless.
You underestimate the Ameirican people and the amount of TV they watch, they know the candidates, its all they talk about on the tube these days, I think your argument is probably coming from a positon of backing a candidate with no traction and hoping for some sort of change in the months before the election.
don't tell the rudyfans that!