>>543252690
That's what they did, but their family was huge, even with the park full of guests, it didn't satiate everyone enough to survive on it. The hemobars were made in order to preserve as much blood as possible and to have way more than usual to feed everyone by converting it into nutrition bars, so the donated blood could be consumed way later, and transformed into bigger quantities.
The issue is that bloodfiends are feeding off the feelings of the victims they drink from, so if the blood is left around for too long, those feelings will vanish. In terms of nutrition they are covered, but they aren't truly feeling satisfied on a fundamental level for their disease, which Bari equated to Loneliness.
Don Quixote and Sancho both enjoyed stuff relating to fixers, and had the equivalent of a dream or something to live for beyond just survival, the others were just doing their part in park but it wasn't truly something they enjoyed doing deep down, Barber enjoyed her dresses, but they were being made for a specific purpose, and not because she wanted to make them in particular, Priest wanted to make it work but similarly he didn't really enjoy the situation, especially since he had to hear everyone's laments, and Dulcinea wanted to be fawned over, but I guess the angle of the park wasn't enough for her.
Essentially, it seems like if a bloodfiend finds something they genuinely enjoy doing, that has nothing to do merely living for survival, their thirst will be severely diminished.