Why do women over 40 shop in the juniors department?

Is it because your thin? You want to look young? Because the clothing is cheaper? I think most women over the age of 30 who shop in juniors look unprofessional and look even older. Granted I might get a pair of juniors PJ's but I would never wear that style clothing again and to work or out in public. What is with this trend with not wanting to grow up?