Outside of the NEC and a few other "corridor" operations, Amtrak is an occasional "accommodation" service for those who have no option other than driving, or who want the first-class trip. Long-distance private bus lines no longer serve most small towns - as deregulated private operations they dropped all that stuff because it didn't make money. So Amtrak, along with other government-run or subsidized bus operations, is the only non-car transportation service many rural places have. As the Greyhounds of the world know, that kind of service can't make money - it's a social service with an incidental transportation aspect.

FWIW, air service to smaller airports is also publicly subsidized, either through a federal program or by local funds. Nobody would fly into Modesto or Visalia just for the fares.

Tax credits don't work well as operating subsidies. You need to cover operations with cash for payrolls and other expenses as they happen; tax credits, at best, come back quarterly. For money-losing operations that are deemed necessary, direct subsidies or actual public operation are usually necessary.

AAF has been carefully designed to hit the sweet spot for the service they plan regarding cost, and IIRC they're getting most if not all of their up front money from private sources. Apparently, for what they need, the political and bureaucratic hassles of getting federal loans outweigh the potential interest cost savings - savings that are probably minor or nonexistent in the current financial markets. Tax credits in their case would mainly be a bonus.

The danger of relying on the FRA (federal) loan program is demonstrated by Desert Xpress (the real HSR alternative for LA (well, Victorville initially) to LV) - they had a business plan, but the politicians that don't want any successful passenger rail service, let alone real HSR, stomped on FRA and killed the application. Which killed the project, because real HSR requires a much larger investment up front with a longer payback (though their plan did demonstrate payback) than adding low-end HSR to a reconstructed but still conventional rail line - resulting in the financing being too expensive if done privately. Would tax credits help? Don't know. The company's web site is still up ( [www.xpresswest.com] ) but hasn't been significantly updated since loan processing was "suspended" by FRA in 2013.