The problem is that the people who do the research and the people who publish the research are not the same people. The people who do the research may be funded by the government, and thus the general public, but the people who publish it are not; they are funded either by the dues of their organizations, by subscriptions, or by advertising. Or in a few cases by having the authors pay for the publication. Only in the last case would it be fair to have the publishers provide the paper for free, because they could pay for publication out of the same grant that covered the research, and thus the government would be paying for both the prosecution of the research and the publication of the research.
You cannot pay the producer for production, then require a third party distributor to distribute the product to anybody who requests it for free, regardless of whether the product is tomatoes, gasoline, or research results.