The airlines look at total revenue per flight to a certain destination(HNL)to determine if it is a "profitable" run for them.
It is well known that Hawaii is the #1 destination for redemtion of FF awards. Thus, FF award travel cuts into total revenue for Hawaiian Flights.

I guess with the word "subsidise" I was a bit unclear, I feel the airlines should set up an internal accounting procedure so that award travel is treated as "revenue" in determining the "profitability" of a particular route.

I fly between the mainland and Hawaii 10-12 times a year and very seldom see an open seat in coach or up front(even off season). Please believe me when I say there is room for more lift and/or larger aircraft.