I don't think airlines do anything for prestige if they are going to lose money in the process. Declining food service is one example of airlines forgoing costs over maintaining prestige.

I. suspect these ultra-long haul flights serve a need and leave full most days. I have not experienced a flight that has not been sold out in several years. Every time I get on a plane, I hear the announcement, "This is a full flight. If you cannot find space for your bag, please let us know so we can gate-check it."