The government once they found that they would have to pay a very large sum to take care of every child out there whose legal father decided to no longer pay once he found out the child is not his (and/or just to spare the child from all the drama, once the court says yes you're not the biological father but you're still on the hook).
I think it was after a survey on cheating and promiscuity, but I'm not sure of this since this was just something I heard of from other people and I can't find much from a quick search on the internet.
The reasoning is that the priorities of the child come before the priorities of the father, so in order to protect the stability of the family you are not allowed to know.
As to who supports this, a lot of women seems to be in support of it (they have nothing to gain from opposing it) and all the people who seem to 'think of the children'.
Some politicians claim to be against allowing the paternity test on the ground that it is against the values of the republic since it's an aknowlegment of the importance of relations blood, genetics, and race(ism), but these are the words of politicians so they don't mean much.
