The German government has passed a law which forces private insurance companies to accept any customer who applies for health insurance. However, it turned out that many of these newly insured don’t pay their insurance fee! Now they get free insurance because the law does not allow insurance companies to stop their service.
This is just one trick to get health insurance without paying for it. There are numerous other tricks which people play to get mandatory health insurance for minimum insurance fees. This is a major problem of mandatory health insurance when all people start to play tricks instead of paying their fair share.