heh. Then my DEN-NYC flights fall in the same category.

You're mixing a few apples, oranges, and maybe a couple of pears. Entropy could probably get F seats connecting through IAH or CLE (don't know the exact dates, but IAH,CLE->SFO are showing F seats when EWR->SFO isn't). In this instance CO's F availability seems equivalent to your experience on NW.

It's the true transcons that are the problem, and NW doesn't offer those. I earned my CO status mostly on A fares EWR->SEA,PDX,SFO, and can tell you that FC on those routes is in a completely different class than anything NW runs in the lower 48, particularly on the BF A/C.