I don't draw nearly enough (let's get that tiny bit of painful honesty that out of the way right now!), though I am trying to discipline myself to draw more often. I used to draw regularly, when i was attending frequent lectures. Now I find that I would rather paint, than draw--and although it is important to work on the paintings, regular drawing keeps the ideas flowing, helps to "develop" (improve) the ideas, and develops the "chops" (skills...does anyone still say "chops", anymore?)
Keeping a couple of sketchbooks handy, helps. (I probably have--literally--hundreds of sketchbooks. While its easy to just grab one off the pile every time I deide to draw, it's better to work my way through a book or two, since that allows me to build on earlier ideas--and keep track of the good ones.)
Several of my recent paintings, including the three 15x45 inch panel spider paintings, and the small square spider paintings, were created without any preliminary drawing whatsoever (with the exception of "Arachnaverte", which was copied--in paint--from a small original pencil sketch on paper).
And, the results I get from working this way are satisfying--but, only to a point. Lately, I'm finding that if I want to convey more complex ideas (or, more realistic ones), I need to do some pretty involved preliminary drawings.
One thing I've noticed about spiders is that their bodies are opaque, while their legs are quite translucent. This is something I have not tried to capture in my paintings of spiders, so far--but I realize would really like to.
Drawing in paint is fine, and it IS drawing. And, it would probably "do", at least for quite a while, if I wanted only that. But, it does not allow the kinds of revision, rework, erasing, etc. that provides for a through examination of subject (including pose, light and shade, texture, etc.)
So, I'm working on being more disciplined about drawing; drawing more often, keeping track of my current sketchbookin order to "build" up in previous sketches, and really explore my subject matter, to be able to produce the types of paintings I really want to make.