Because currently, it seems like the only thing it’s recording are downvotes. Meanwhile upvotes are completely ignored, leading to pretty much every profile I see having a negative reputation.
Also, I have a very fragile ego and my -6 reputation hurts a bit.
It’s also the opinion of the devs. The fact that it’s boosts and not upvotes is a bug, they’ll get to fixing it, it’s just not top priority right at the moment (since “reputation” doesn’t actually do anything and is just a small number tucked away on your profile).