I can only imagine the tremendous amounts of drawings that great artists produce. I think it's truly what separates everyone into ranges of "talent." As I begin studio paintings, I always think, "How will I approach this painting?"
Of course, a lot of my ideas start with an image that I have in mind. I do believe the composition must come from within and no one can implant a great composition into one's imagination. So I use my imagination to create and enhance what I see, but how do I gather my material to paint?
A lot of artists believe in the power of photography, but photography is merely realism. Bouguereau believed that if you are an artist, then you can do better than realism. He would idealize and enhance features. Even his self portrait from 1879 depicts a noble looking man with moderate features. Even though photographs of him show a short, stocky man with a large nose and small eyes. But he was able to do better than nature and present himself in a better way. That's the point of painting. The limits of Photography can be broken with drawing. If you choose to work from photographs, you are limiting yourself and stopping yourself from drawing.
Drawings are useful for the present moments and for future works, which is why I titled this post as such. If you see a plant on the ground that would serve a purpose, stop and draw it. Don't immediately allow yourself to take the easy route of photography. Every time I draw, I feel my hand connecting to my eye. I would liken it to the passive activity of watching TV versus the active reading of a book in that one washes over you like a wave and the other requires skill to enhance learning. Developing an idea, learning through the process and enhancing life through drawings are the high road.