Maybe it's a hold-over from when syphilis was a REAL problem. The 36,935 new cases in the US in 2006 wasn't a big deal, and the 349 of those case that were babies born with congenital syphilis is positively minor.

There were 2,766 reported cases in the whole of the UK in 2006.

All sarcasm aside, there is NO reason for a baby to be born with this when there are tests and treatments. Maybe it's easier to screen before marriage if you can't be sure a mother-to-be will receive prenatal care at all.