It's a false corollary to expect lowered taxation to immediately equal greater spending - especially in times of economic flux, that sort of government action mainly encourages /hoarding/ behavior, which isn't good for the economy's health.
On the other hand, direct investment in startups gives an immediate incentive to spend - spend and grow.
Spending more on public goods like health care helps - the money we'd save with a public option is obvious to anybody that isn't a far-right ideologue. But that's /saving/ wealth, not /creating/ wealth. When you finally snip away all the excesses and waste generated by the current model of health care coverage, you still need something to pay for the cost of the improved system itself.
Citation needed?
> Spending more on public goods like health care helps
I think most of us are fine with government supporting the public good, building infrastructure, etc. But it's a little sleazy to directly fund startups. I mean, if my uncle donates to Obama's campaign, will my business get special treatment? (That's how it works here in Illinois, or so it seems...)
Hoarding usually means saving, and saving usually means investment, since most people save in interest-bearing accounts that one way or another turn out to be investments. You definitely want a good mix of investment and spending (not too much or too little of either) but it's rather ham-fisted for the feds to invest the money themselves.