Looking back in time, my location drawing has been a fairly steady transition from black and white line drawing, through line and wash, and towards painting on location. Mostly I see this as a natural progression. An 'improvement' from drawing towards painting. I think most people would feel that paintings are somehow more challenging. A 'higher art' than drawing?
There's some biological reason behind it I'm sure. A painting, being tonal, can tap into the eye-to-brain function and convince us we're looking at reality. But, oddly, that's why I love line work. Because it's not such a straightforward illusion of reality. There's something about an 'unfinished' sketch that really appeals to me. It's partially the speed of execution (they are more fun for the artist - no labor, just free-flowing seeing), and partially the way line is both specific about detail yet an abstraction at the same time. A line drawing conveys so much, so compactly. I can't get over the joy of that magic trick. How does it work? That a drawing can make us see an object in our mind?
That's why I'm currently hooked on washable ink.
It really is the best of both worlds. I'm convinced that this approach is the ultimate sketching tool. The Lamy fountain pen, (or washable dipping inks - Lamy in a bottle, or Private Reserve) I'm using these days, combined with watercolor. It's so much fun. Melting your drawings, into paintings. (Yes, yes, I've said it all before - but I love this so much, it's a mini-obsession right now). I've recently discovered that the paper matters a great deal. I'm getting nice results with coated stock, such as this 8x8" watercolor book by Hand Book.
Here's another before and after showing the drawing, the melting with color, and the results.