Some lines are too fine and too straight for a round brush. This angled liner brush has short, firm bristles arranged in a special way to lay very thin, controlled lines, so scratch lines, markings and small freehand drawings stay crisp.
Yes — this shape is also used for eyeliner and makeup detail, which is where it comes from. The same fine, angled edge that draws a clean eyeliner line works for scribed lines and panel markings on models.