We draw to know the subject.
The ability to draw must and should precede the ability to paint. The craft can only work in that order. But for painters the painting must subsume the drawing; encapsulate it. The color and form takes front row. That's one reason professional and very famous painters change their works in midstream. Their perfect drawing disappoints as part of the whole painting thus they revise (the drawing) and then the painting. The whole of the painting and all it entails is foremost - MUST be foremost.
It is natural that there are more competent drawers than painters - it's easier. If we start to assign the source of a failed painting there are many reasons where we may truthfully place blame. Yes, the Impressionists were weak with their drawing - just like most painters today - especially in the Western states - or at least the western subjects. I personally know many famous landscape painters making over $300,000 a year that can't draw a person. Rocks are forgiving. These guys know everything else very well. They can design, they know paint handling, they know aerial perspective, they know core shadows and by God they know design and composition! These things carry their lack of ability to draw well. It would not be so if they did still lifes, interiors, portraits or figures.
Try to make a living doing charcoal drawings. The best there is would find it tough if not impossible without sales from oils. The market for b/w is weak and the supply is vast.