I fly these segments a bunch of times a year and find them flown by empty 767's. While I'm sure there's a lot of cargo down below, these flights probably don't have the passenger flight loads they'd like to see.

A few weeks ago I was on a NRT-GUM which was pretty much empty in the BF cabin; there was me, a few other passengers, including non-rev's. I sat in an empty row with the row behind me empty and the row in front of me nearly half-empty. And on a recent GUM-HNL, it was a little more full...but still didn't have many passengers on-board in Y or J.

If they can load up a 777 with cargo, that'd be great... but otherwise a 777 on those routes becomes a non-rev dream with huge forward cabins (and rear ones, for that matter) with few paying passengers.