Also do we need them?
Governments like to keep statistics on when their citizens are born and when they die. A birth certificate is one of the ways you prove your identity.
Come on, you’re pulling our legs.
I’ll take the question at face value.
The US constitution contains a couple of clauses that make birth certificates a very good idea. One is the bit that state that anyone born here is automatically a citizen, and the other is the one that gives an age minimum for running for president. Without proof of where or when you were born, you could not claim citizenship or prove your age. Before birth records, it used to take a convoluted process to establish things like this. You had to get witnesses to swear to knowledge of your birth, and produce baptismal records, if you were baptized as an infant. If your mother was alive, you could get her to swear that she gave birth to you here, and if she still lived here, it helped. If she had, say, gone back to England, because maybe she was never much of a separationist, and after your rabid pro-revolution father died, she wanted to go back to the place she was born, you had a problem. Unless, of course, you lived in one of the places with a birth registry.
Ironically, while a birth certificate provides evidence of where and when Ike Witt was born, it does little to “prove your identity”. A person flourishing a piece of paper that turns out, on inspection, to be Ike Witt’s birth certficate may or may not be Ike Witt. The certificate may help to show that he isn’t Ike Witt if, e.g., gender or age or both are obviously wrong. But it can do very little to prove that he is.
Different countries use them in different ways, or have other documents in lieu of. For example, in Spain if I asked the Civil Registry for a birth certificate, the worker might or might not give a rolleye before asking if I mean a Fe de Vida… a document stating that according to the records they have, I was born on DD-MM-YYYY in Such and such place to This and That parents and am alive.
This kind of difference can sometimes be a pain in the ass when dealing with bureaucracy in international contexts.
According to law of different nations or countries its a proof/identity of he/she residing in this nation .
some times process to make other docs like Driving Licence, Passport, Election Voter ID it is mandatory to submit DOB certificate and it proves you are the citizen of country.
I we lived in a world where people didn’t move around and everyone knew who their neighbours (and their neighbours’ children) were, where each such community could administer communal responsibilities for each other’s safety and welfare and ensure everyone contributed as they could, then there would be no need for documentation and formalisation.
But once you have a mobile population with expectations, then you need formal systems to administer law, order, and other public services.
As noted above, there’s an ongoing issue about the complexities of what constitutes “identity” and what constitutes sufficient authentication of it for different purposes, but that’s a reflection of the complexity of the social system.
True, but people don’t just materialize out of nowhere as adults and start flourishing birth certificates. From an early age, a record of consistent documentation and personal history is built up that is unique to that person. For most important official purposes that corroborating documentation is required. Someone who appears out of thin air at the age of 35 with a birth certificate and no other documentation or history would definitely attract some official interest!
Sure, but what the birth certificate proves is Ike Witt’s date of birth, place of birth, gender at birth and parentage. It tells you nothing about his current identity; not even whether he is still alive (or, nowadays, still presenting with the gender that he presented with at birth). So, the ability to produce Ike Witt’s birth certificate does not show that you are Ike Witt.
Which is why, when you apply for a passport, they won’t accept a birth certificate as proof of your identity. They’ll want a birth cert plus proof of identity in the form of something official with your photograph and your signature - your birth cert has neither - or an identifying witness who has known you for at least two years, plus your own declaration as to your identity, made under penalty of perjury.
The birth cert isn’t wanted as proof of your identity, but as proof (or an element of proof) of your citizenship, which will be based either on your place of birth or your ancestry.
It used to be the case in the UK that a birth cert was sufficient to apply for a passport, which then opened the door to anything that required proof of identity.
In Day of The Jackal, Forsythe describes how his hit man gets a passport by first applying for a copy of a dead baby’s birth cert. Amazingly, this ruse still worked 32 years later. These days it is a lot harder to prove that you are who you say you are.
All of which is perfectly true and no one has disagreed with it. It happens to be true that the birth certificate is both a foundational document for many purposes and also fairly useless in isolation for an adult without corroborating documents to establish identity. Both of those things are true without contradiction.
But proof of identity can be all sorts of things. Years ago, my boss, a man in his 50s with no driver’s licence and no documentation other than a birth certificate, needed a passport. I went to the office with him, and, having known him for most of a decade, I “swore or affirmed” that he was the man named by his birth certificate.
His stories over the years, including stories of his childhood, seemed consistent and convincing to me. 
He got the passport.
All of which raises the point that right now in the US we really don’t have a very air-tight system for identity of natural born people. Even for those born today they accumulate bureaucratically-verifiable identity only slowly and uncertainly.
Unlike what somebody said above, there really isn’t much official scrutiny of people with unusual records.
Whether all this is an open invitation to criminality & evil or an essential element of our remaining freedoms is in the eye of the beholder.
They could put DNA info on your birth certificate now. Then if anybody questions if it’s really you, they make you take a DNA test.
As I remember, official copies of birth certificates are embossed by the issuing authority. It’s not proof against counterfeiting, but it takes more than a copying machine to do so. I don’t imagine it’s a big problem since even a little litho press will turn out bogus SS cards on the cheap.
So our merchant sailors don’t get impressed by the British into their European wars.
I’ve heard of one case in which the ownership of a rather valuable piece of intellectual property was disputed because the author’s birth certificate could not be found, and it was uncertain whether or not he was over 18 when he signed the rights over to the purchaser.
In the Good Old Days, the government mandated the Church of England to record births (well, baptisms), deaths, and marriages. Somewhere around the early 1800’s (1837?) the government decided tot take over this job, recognizing there was more than one Church and a number of people slipped through the cracks, so a more comprehensive system was necessary. The process I assume was similar in many other European countries - as social evolution and secularization replaced the churches in many social support activities with the government, the government saw the need to become organized, and appropriated many of the tasks that fell to churches; ie. Bismarck enacted Sickness and Old Age pensions for the German state in the 1880’s - presumably someone saw the logic of needing to be sure whoever you were paying was truly entitled to their pension - in citizenship and age, and to prevent double-dipping.
Presumably the USA, being secular from the start, took on the tasks like registering births that normally fell to the churches. Also, since the constitution mandated a census every 10 years, it was obvious someone saw the value of tracking all these details of who was who and since when. For example, the USA had conscription during the Civil War - someone had to keep track of who was eligible and not, and how to select draftees.
So it’s not a method of being “owned” by the government and other entities?