Are quick drawings and paintings artworks or just studies? Are they value at all?

A lot of drawings of old masters have an immense value nowadays but looking at contemporary artists drawings, are they such important?

Why don’t contemporary artists exhibit mostly their drawings and experiments, just their final masterpieces?

Self portrait Scrying

Scrying – pencil and chalk, quick drawing on paper

Drawing from imagination

Drawing from imagination, pencil on paper

Spiritual

Spiritual, Mixed media on paper