They might commit some crime in 15-20 years' time though.

Criminals are actually fairly rare. Once everyone's genetic data is captured it's actually more likely that any given individual will be falsely accused of a crime by lazy cops and prosecutors. "You coughed on a window adjacent to the crime scene, some time in the week before the crime! Guilty!"

I absolutely agree, and I find this sort of total surveillance mentality completely abhorrent. My comment was mostly meant to illustrate the sort of reasoning that goes with people seriously suggesting that collecting newborn DNA is a good idea.