Okay, trying to not get too far off on a tangent, I miss Brock but the entire cast needs to be changed out!
As for animals in the world of Pokemon, I blame it on the series being stylized and geared toward children. You did see the occasional "normal" animal in the world of Pokemon, although rare and mostly early on. Notice how animals and insects are replaced by Pokemon, but no other lifeforms with Pokemon equivalents. We don't have only Pokemon substituting for fungus, micro-organisms, people or plants, and yet Pokemon that could exist. It is just the writers wanting to show off Pokemon.
Now I am aware that early in Pokemon references were made to eating them, but that was before they were so "humanized" and I don't know if the original Japanese refers to it this way...