I don't think filling FC with paid customers was ever a precondition to the profitability of a domestic route (exception being the significantly less dense premium transcon aircraft configurations).

But filling it with business travelers that skew toward more expensive (i.e., less advance purchase) fares certainly is important, and this schedule is pretty terrible for business travelers (IMO). Not to mention that business travelers want options, not one daily flight.
It's what has skewed me away from AA for years on the secondary transcons (or near-transcons) when I used to do those fairly often for business (e.g., SAN, SEA, LAS until recently, etc.).