Is it a matter of supply and demand?
Specifically, the American public isn't placing a demand on the candidates to supply a space policy. Judging from some of the poll results we've seen over the past few years--the lack of interest, the gross misconceptions--are we lucky to be getting what little we are from the candidates? It'd seem that the mind of the public, and hence the votes, are elsewhere.
I guess that's a long-winded way of saying "agreed."