Why should you only mark the golf ball with a golf ball marker in accordance with correct golf behavior?
Marking the golf ball with a flat object or a designated ball marker has the advantage that these two objects are very flat and should a ball from a fellow player unexpectedly roll over it, this golf ball is only slightly deflected. A golf ball marker and a coin are also inconspicuous and do not interfere with golfers executing their putt.
A tee or similar, which is often used to mark the golf ball, often distracts the golfer, prevents a successful putt and does not correspond to golf behavior. Using a golf ball marker to mark the golf ball also prevents damage to the green. Other objects, such as a tee stuck in the green, can cause damage.