don't you know not everyone has a car? don't you know the thrill
of doing it outdoor instead of in the car? you wanna be
comfortable, stay at home or hotel lah.
criminal offence? then police should be patrolling the park more
often i guess. the most is warn you not to do it in public, unless
someone complain lah, but by the time you would have already run
away.
lastly, what makes you think the dirty things cannot enter your
car? i know of more dirty things who died on road than at secluded
public places.