Prenatal paternity tests can be expensive, but if you did it when the baby was born along with some of the other routine tests they do then it wouldn't be very expensive. If it became mandatory then the tests could become streamlined and less expensive.
You can always get one if you feel the need.
Okay. This is exactly why it should be mandatory. If people can be lied to for 30 years and never suspect anything then they clearly don't just feel a need put of nowhere. Also, look at it this way, if it was mandatory then you wouldn't need an excuse or explanation of why you want to get one.
A scenario: Girlfriend/Wife a has baby. You both are very emotional and scared about the future. You ask for a paternity test in the midst of all of this. GF/Wife doesn't take it well and wonders why you dont trust her. That could lead to resentment. Test is done. Baby is yours. Now all that's left is the resentment and an overwhelming feeling of "why wouldn't he believe me!?" Which is justified.
another: S/O pregnant. Test is mandatory. No one is the wiser unless the guy isn't the father. No resentment. No distrust.
Third: Pregnant. Mandatory test. Baby isnt yours. You know this from the beginning. You get to think about what you want to do with the information, but are happy this didn't happen decades later after you have invested your life into building a family one lie.
Which are better? Is that kind of information worth a few hundred dollars? It could be priceless. If it were mandatory insurance would probably end up covering it as well.