It's an objective, publicly available piece of information. Birth records aren't secret, or in any way protected from public view.
I'm not sure that if you knew my name and the approximate year I was born that you could find my birth record. Probably depends on whether there was a birth announcement in the local paper when I was born and it is currently searchable on the internet. I can tell you that I can probably count on one or two hands the number of people who know me who know the city and state I was born in. I have very good friends who know my birthday but have no idea where I was born. I took a look and my state of birth would not allow you to get a copy of my birth certificate, so if you knew the place but not the date, you'd be out of luck there too. So birth records aren't really as open as you might think. Try looking up your own via an internet search. You might find it's harder to find than you think. This is a good thing as one of the ways identity theft gets done is via knowing a person's birth date and year, but that's in part a factor of greed in businesses being willing to give credit cards, loans, etc. on insufficient proof that you really are who you claim to be.