[roughly]

There’s a couple factors - one is the payoff time and risk levels make basic research difficult for even businesses with long time horizons to engage with, and American businesses are notoriously short term. The other is that there’s a large public benefit to making the fruits of that research widely available by way of risk mitigation - it’s commercial companies that take the research over the line, but making the research public allows multiple companies to take a shot at commercializing the results,

In general, considering the government and public money to not be part of “the economy” will make your internal models less performant - the public is an actor in the economy and so is the government, and both make decisions on the basis of their needs, values, and resourcing. Those entities seeing higher rates of return for their investment than other actors like private companies is absolutely consistent with, for example, different companies seeing different rates of return for the same investment dependent on their needs, resourcing, and constraints.