Mathematics is the abstract science of number, quantity, and space, either as abstract concepts (pure mathematics) or as applied to other disciplines such as physics and engineering (applied mathematics). Research indicates that children who know math are able to recruit certain brain regions more reliably, and have greater grey matter volume in those regions than those who perform more poorly in math. Math helps kids analytically and allows for better reasoning abilities to think logically about a situation(s).
To live in a mathematically-driven world and not know math is like walking through an art museum with your eyes closed. Learning and appreciating math will help kids appreciate things that you would not otherwise notice about the world. It also is the basis of numerous science and engineering fields. And more importantly, it's a universal language.