In a lot of the world Jan. 1 is everyone's birthday. Or Dec. 31 (The article cites Somalia, Sudan and Vietnam as other examples, but I have been to several other countries where the majority of the rural population has the same issue). It's not really a big deal - some people just don't care what the exact date was that they were born. It seems a bit culturally imperialistic to impose that norm on a lot of issues (aid distribution, human rights, passport standards, etc.)
This is the quote cited from the UN report, which makes a case for the importance of registration pragmatically:
>“Birth registration is instrumental in safeguarding other human rights because it provides the official ‘proof’ of a child’s existence,”
... but it begs the question for any parent in this situation: "Why do I need proof, my child is right here in front of me?!"