>>12992
Horse teeth don't continue to grow, horses just have very long teeth that slowly slide out of the gum over time. They are made to wear away because horses have to grind grass all day. When horses get old the teeth can completely wear away and then they can only eat mush (it makes snuzzles yucky). The reason humans have to brush is because we eat so much sugar and other processed carbohydrates which turn into sugar. Bacteria converts sugar into acid which dissolves teeth (not unlike the process where yeast make alcohol or rise bread). If we didn't eat processed food and lived shorter lives like our ancestors brushing would basically be unnecessary like it is for horses.