Getting them to take it down is more trouble than it's worth, even if it works. You'll be playing whack-a-mole all day long. Ideally you want them not to use it

Getting them to take it down is more trouble than it's worth, even if it works. You'll be playing whack-a-mole all day long. Ideally you want them not to use it in the first place, and a visible watermark accomplishes that.