How many is "lots of" because it's real hard to find concrete cases of this outside of the handful of high profile ones that reddit MRAs like to parade around whenever they get a chance to bring it up.
But regardless, this is consistent and a well-understood compromise not an accidental injustice. The priority is stability in the child's life above absolute fairness for the adults. If you occupied the role of parent to a child, you may have to pay child support regardless of biological connection.
We've settled on this approach over the alternative because when unfairness occurs, it is for the adults to experience not the child.
It is likely a few percent, but having draconian collection processes and lower levels of enforcement of child support fraud are issues. There have been problems with these draconian laws being exploited where the 'Mom' takes her judgement to a new state and starts collecting all over again. While it would be fraud to sign the initial affidavit, it can be tough for the target to shake it off. I have talked to two men whom this has happened to. I am in no way saying legitimate child support claims should be upheld but automated punishment that exposes the target to arrest rather than it being at least at first a civil court process with maybe failure to appear as part doesn't seem to help anyone but a vindictive or manipulative ex.
It sounds about equally as moral as forcing some complete stranger to pay the child support(which does not sound moral).
The government could provide the child support. I would argue that forcing the victim of a paternity scam to continue paying for the child that is not theirs just continually revictimizes them.
But regardless, this is consistent and a well-understood compromise not an accidental injustice. The priority is stability in the child's life above absolute fairness for the adults. If you occupied the role of parent to a child, you may have to pay child support regardless of biological connection.
We've settled on this approach over the alternative because when unfairness occurs, it is for the adults to experience not the child.