I don't know the reason for this but if I would need to guess then it's mainly about not being afraid of being sued to bankruptcy in the rare case something happens. Though I really can't remember reading about anything happening to a child in a news paper, so I assume (or let's say hope) no to drastic accidents happened on German playgrounds in the last years.

Never considered that health insurance might be an issue to come up with those super safe playgrounds. But yeah if your retirement is endangered by you kiddo climbing up a monkey bar set it might feel way more dangerous. Could maybe also explain to a certain why most European playgrounds are more adventurous then their US counterparts.

EDIT: Also tbh I really do think it's a good thing for kids to be able to climb up on things and explore stuff that might look dangerous especially to the small ones and learn how to behave their and how to overcome those situations and also learn to improve their body control at the same time as well.