Well, the rule does say "including but not limited to powder, marker or paint." What other type of marker is there other than magic marker/sharpie? 99.9% of bowlers wouldn't care if the ball gets used in sanctioned competition, but there will always be that 0.1% who files a protest when they lose and want to take it out on someone.
I was bowling in a tournament recently and a guy on our pair used acetone to clean his stuff during practice. It smelled like a paint shop in the settee area even after moving lanes after each game because he continued to use the same towel during the tournament. No one cared despite the use of acetone being a HUGE no-no.
Chapter 8 also states that the ball MUST have the original brand name/logo, ball name, and serial number on the ball. How many balls are out there being used after multiple resurfacings where the engraving of the make and model is partially or totally gone? I used my Ebonite Adrenaline Shot for the the first time this morning, and after 2 games the orange engraving in the "A" in Adrenaline has already started wearing away. 100 games from now who knows what will be left on the ball?