Obviously the answer is both. Artists have always drawn whether as preparatory studies for working out problems in a painting, which can become finished pieces in themselves,as a habit to sharpen our ability to see, or as finished pieces of art. Most artists though have a craving or desire to record what they see, and using graphite, charcoal or pen and ink are spontaneous ways of doing that. I've drawn a lot in my years of trying to figure out who I am as an artist. I've also had stretches where I don't draw much and my work suffers for it.
Most of my drawings are preparatory, trying to figure out compositions, exploring different ways of seeing scenes from life or photographic reference. Studying different artists and how they draw is essential. It's a way to see into artists thoughts and struggles. And don't confuse elaborate finished work as being more important then spontaneous, quick gestures which usually have more insight and freshness to them.
I've posted drawings from some of my sketch books used for drawing from life. Some are in hotel lobbies,airport terminals and malls. They are primarily drawing for drawing's sake. There is a joy you get from just drawing when you are responding quickly to what you see.