I feel like this item in particular can be argued by some as an "accessory" type of item versus a "clothing " item. Personally, I don't like wearing leggings as pants alone. Maybe I haven't found a pair that I'm comfortable enough in, or feel cover me well enough that I'm not constantly checking to make sure no weird lines are visible, or they're so thin of a material, depending on the lighting, you see a lot more than you bargained for when putting them on.
Of course, if you're in a jam (or manage to get jam on you), and need a spare pair of pants for some reason, I suppose you're better off wearing them compared to nothing (though this all depends on the situation, such as where you are when you need said pair of extra pants-if you're at home forget about it, be free and just go pants-less!...if your roommates don't mind that is...).
All of this aside, I like leggings, especially in the colder months, because it's not only another layer for warmth, but it can add color, texture, or just general pizzazz (not to be confused with pizza) to your outfit easily. They also allow you to wear "summer clothes" like shorts or dresses without freezing your legs off.
Have a cute pair of shorts that would look great with your new sweater and boots, but its 40 degrees out? Throw on some leggings!
Itching to wear that sundress from last summer but it's less sun and more breeze now? Legging it up! (I don't know if that phrase actually works as a thing now that I've said it...)
Wanna show a little leg while at dinner tonight, but not enough to risk the pain of goosebumps caused by the cold air? Wear these gorgeous leggings to add a layer of warmth, but still feel like you're dressing up!
Leggings are also great for working out in because there is no extra material to worry about tripping on, stepping on, getting your toes caught in if stretching out (yes, these are all based on experience with wide legged yoga pants...judge away)
Leggings are not only useful for their fashion aspects, but in weather based emergencies as well. I always take a pair with me in the winter just in case my car breaks down, and I need another layer because it's REALLY cold out (its happened before, and I was incredibly happy to have a pair of leggings to put on under my jeans while sitting in a dead car while it was -3 degrees out in the middle of February).
So clothing, accessory, or whatever you want to categorize them as, leggings have a lot of benefits and multiple ensemble functions in my book.
What is your favorite way to wear leggings?