Unspoken ethics do exist.
Consider, there are almost a hundred guys regularly on tour. Some are liked, some not. Some have friends, some don't. Some get regular practice partners, and lots of guys lining up to be, some need to beg the event organizer to find hitting partners.
So, you play using all the gamesmanship and tactics. Lots of pure hitters would look down at you. Lots of pure hitters on the tour.
Think of yourself. Would you hang around a shyster/flim flam guy who uses all the gray tactics when he plays a match?
Or would you rather hang with a pure hitter, who plays the game clean.