Ruto had breasts because the artist that came up with her was a real manly man. Manly men know the only way to tell a woman apart from a man is massive mammaries! Therefore all female members of anthropomorphic cartoon characters require breasts.
If you're not a manly man, or it's anatomically impossible for your character to have breasts then you can substitute long eyelashes, skirts, hair bows, and big red or pink lips.