I cannot say this enough times. LEGGINGS. ARE. NOT. PANTS.
They should not be worn in restaurants. They should not be worn in the mall. They should not be worn in the streets. You should not wear them at all. Unless you are jazzercizing in the comfort of your own home.
I don't know where this pant impostor epidemic came from, but I want it to go away. It doesn't matter if you're a size zero, I do not want to see your lady bits on display while I'm strolling through the produce section. Leggings were initially designed to be workout clothes, so possibly making sweatpants acceptable in public was a sort of a gateway drug.