IIRC, the Starlight began as a 3 times a week train oriented mainly at tourists. Then, there were short trains on the "off" days between the Bay Area and LA providing daily service where there was some regular demand for it. That was back in the "rainbow" days before Superliners.

These days, a similar service might be Sacramento-LA daily, with through trains 3 times a week for the tourists similar to the way the Sunset runs and perhaps buses on the "off" days for the basic transportation traffic. But there *is* demand for the daily train, just based on the fact that it's usually sold out or nearly so. There might be enough for more than one if somebody really operated and marketed it properly (yes, I know, but it's on UP). But we can't know that for sure because Amtrak's accounting and other information systems don't permit independent analysis.

Really, Amtrak as a whole needs a corporate restructuring, not just the long distance trains. It's never been run as an actual business despite being set up like one. Politics always drive the decisions. But it's not a government agency either (courts have recognized that several times). Amtrak needs accounting that follows either standard (railroad) corporate or standard governmental principles (pick a side, do it right, and make it public). For now, nobody outside of the C-Suite at Amtrak really knows what things cost and what the receipts are and where it all comes from - if even they know. Passenger trains being passenger trains, the service will never actually make money as a whole, and with transparent accounting it might even look worse. But as with all transportation (especially passenger transportation) modes, some government subsidy is appropriate in order to gain the benefits of the mode (ignoring hard-line ideological positions for the sake of argument).