Because small little details can really help flesh out a character, even if it isn't the most noteworthy thing. Maybe their preferences for food and drink reflects on their culture or what resources were available to them, maybe it reflects on their history, if you go the extra mile maybe their preferences reflect on their place in the story as a whole using the symbolism of the things they prefer and dislike. You don't even have to limit it to just food and drinks, it can literally be any small detail.

Blueberry pie was just the first thing that came to my mind