it stops all those people that walk around with pocket fulls of sand who's intention in life is to deposit it in vulnerable engine orifices. What do you mean you've never seen them !!!! There are dozens walking along every street acting all innocent.
Plus you must have seen all threads about sand and stones being put in all those BMW engines, the forum is rife with them.
And another thing, i've never had to use any of the special tools supposedly required to open them - Just wear dry workshop latex gloves, push down on the cap and twist and off it comes
Hey.... don't forget you ride a BMW... that means the rest of the world views you as a stuck-up and uncaring... this makes you a much bigger target of the hidden sand saboteurs...