Sketchiest my sketches get
The wips I usually send out to people are almost finished pieces compared to these, though both can still be considered sketches
You can treat sketching as another tool, like a brush or lasso tool; a sketch does as much as you want it to do. The more lines you use, the more complex a piece will generally be (though the placement of lines can have the opposite effect), and the less lines, the simpler. The number of lines you use, and the degree to which you finish a sketch depends on many, many things.
Skill level, hand coordination, desired finishedness, number of passes over a previous sketch, and lest we forget that different parts of an image can have different levels of finish depending on what you're most interested in.
All this to say, sketching is a really diverse thing when you start to view it as a "why do I do this thing" kind of thing. I'd say it's where the majority of learning and stylization occur