There are numerous reasons to avoid dairy, including the fact that most of the world's adult population is lactose intolerant. Though the inability to digest lactose sounds like a defect, it's actually the normal state for adults - while the ability to digest lactose is a genetic mutation. Dairy is also high in saturated fat and has been linked to prostate and other cancers (source). Oat milk contains fiber, is low in fat, and does not contribute to the inherently exploitative and cruel dairy industry.