Personally, I think that there is a not inconsiderable measure of conflict inherent to the idea that biological parenthood should necessarily coincide with financial responsibility and actual parenthood.
I know for a fact that they are three entirely different, often all-out conflicting things.
As it turns out, I was also once subjected to a biological parenthood claim. The DNA test clarified matters and exempted me, but that sure gave me some food for thought.
Somehow it just doesn't make much sense to decide whether I am responsible for my sexual behavior solely on the basis of whether there was a pregnancy. Or to put it another way, it is not always or necessarily fair for the woman and child to saddle them with a permanent relationship with a man who has to be pressured by law into wanting to be a part of their lives.
And, of course, there are definitely fraudulent claims and manipulative pregnancies.
All in all, well meaning as financial child support laws can be, they are IMO just too flawed and incomplete to be worth keeping for much longer. I for one long for the eventual establishment of more difuse and merit-oriented models of parenthood.