Expansion, patches. DLC in its current form "provides" content that should have been included to begin with. Many times it is content that has already been developed with the game. Why take it out of the game, and then charge extra for it? To me it is not different than someone selling a car and then taking windows out, selling them as "DLC" at in increased price.
"Well your car works just fine without them, you can drive and do everything it was designed for." Sure thing, you're right. But those windows prevent rain, road debris, etc. from getting in your car when driving. It's part of the car, designed along with the car. But hey, not it's optional to get them, for an extra charge. Aren't you happy?