I believe what makes a drawing “finished” is the artists contentment in a piece. Obviously a piece that is blank in certain areas can make a viewer feel as though that piece is not finished but sometimes things such as that are intentional so it’s hard to definitively say what makes a piece finished or not. I think that once an artist has gotten to the point in their drawing where they personally are happy with the outcome and wouldn’t change a thing is whenever it is finished for them typically. However, some drawings or other work that is considered finished at one point, might later on feel as though they are still missing something. I think other things that factor into the completion of something or not is the reasoning behind the drawing. If you ar turning something in for a grade or making it for someone else, you might be on a time slot to have it “finished” by a certain point. Whereas if you are drawing something just for your own personal pleasure or development, there may be a lot more incentive to not rush it and to go back over time to make changes or add things to it. So basically “finished” to me is a mix of personal opinion and fulfillment towards that piece.