Protecting the kids I think, because if the dad is not known then the mother will have to pay for the child alone (subsidized by the government). In France arou

Protecting the kids I think, because if the dad is not known then the mother will have to pay for the child alone (subsidized by the government). In France around 3% of kids are raised from dads not knowing that they are not the biological father. Personally I think this law is completely unfair but in practice I think the judges will not believe the one opposing the test.