Why do people mark golf balls with Sharpie?
Marking your golf ball is a tool to ensure that you can identify your golf ball and avoid penalty strokes. It can make your alignment on the tee, fairway (when placing is allowed), and on the green much simpler.
The sharpie permanent markers work great but I wash my golf balls often on the course, a clean golf ball is much easier to find. The sharpie permanent markers would wear almost away after a round or two.
A golf ball marker is a tiny object that a player uses to mark the position of his golf ball on the putting green. Because if you don't put a marker, your ball may block another player's line.
Most normal sized ball-markers with alignment lines are allowed; however, the Equipment Rules explain what is not allowed. Ball-makers with alignment aids (lines, arrows, etc.) must be: Less than one inch in height.
According to Rule 20-1, golfers have a right to ask other players to mark if interference is a possibility. “The position of a ball to be lifted should be marked by placing a golf ball marker, a small coin or another similar object immediately behind the ball,” it states.