It's not just "because it tastes good." Those are two separate issues, though somewhat related.

Hachiken is discovering that locally grown food, fresh from the fields, is super delicious. There's a big difference between eggs from a farm or eggs industrially, though the message from the early episodes was that Japan venerates the industrial method that is looked on unfavorably in the West these days. Hachiken learned in the first episodes with both the eggs and the chicken and the pizza episode that there is a clear difference between the stuff grown at the school and the mass produced product he used to get in the city.

The other message is that people these days, generally speaking, have no idea where the hell the food they eat comes from. Hachiken never knew that the cloaca where chicken eggs come from is dual purpose (the specific details of which he ignored once he conflated it with an anus). Or the casualness with which chicken are beheaded for meat. There is a disassociation with common meats and the animal it's from in English, making the problem even worse. While chicken is chicken, cattle meat is beef and pig meat is pork/bacon/ham, sheep is lamb (which is the word for when they're young), or mutton when they're older. There's a lot of kids that might enjoy petting zoos, never realizing the meat on the dinner table comes from a similar animal.

It's less about getting attached to a particular animal and not having the heart to eat it. It's more about having pride in the products you are working on. I happily devour the vegetables I grow in my backyard. If I grew animals, I personally wouldn't have the heart to give them to anyone else. I would have to be the one eating them.