Jeans?!?

Why is that men's jeans come in waist size and length, but women's are just numbered? I'm a shopper, I like to buy nice, pretty things, but as a mommy I don't always have time to try on the nice pretty jeans, and God knows that I could wear a size anywhere from an eight to a size twelve. Why not just make it easy on us mommies that have three crying kids in tow and make your jeans one uniform size??