This has taken me (far too) long to realise – I used to know that painting had to be derived from a first-hand experience and went to some lengths to avoid refining brushstrokes too much to underline the en-plein-air atmosphere (even on-plain-hair in portraits?).
Cezanne, Auerbach, Matisse and Rembrandt all found this out.
A drawing by me is (obviously) a first-hand experience (for me). Drawing the drawing in paint is between the subject and me in a way that drawing directly in paint from a subject can never be.
The paint itself is subject, object and the connection between them.