1-Leggings promote efficiency. Without zippers, buckles or additional straps, leggings leave you all kinds of extra time to do things like quantum physics, backflips or sign language - all things I do, regularly.
Imagine how smart he'd have been if he didn't have to button those pants.
2-Leggings save space. My math skills tell me in terms of volume, leggings take up 43% less space than jeans in a standard dresser drawer, they also take up 63% less space in a closet. And conservation is everything these days because...well, the environment so...there's that.
Leggings help global warming...or hurt it...whichever is the good one.
#3-And finally, leggings are the fashion industry's wingman yet they get no props. A nice, understated pair of leggings helps highlight everything from a hot blouse to sexy boots. They're the ugly friend that make you look better just by standing nearby.
So, in closing, don't hate on leggings. They'd never hate on you.