Agreed - an aircraft that isn't flying won't generate any revenue. Indeed it will cost money sitting around. However if the revenue you generate from flying it is less than the extra direct operating costs incurred through flying then it may be more finacially prudent to leave it on the ground.
A glass half full person might say this makes better profits over the year.
A glass half empty person might prefer to say you are just making less of a loss.
Both arguably are correct!