Birth certificates are kinda in the realms of manfatory and be it directly or indirectly (classed as child abuse in the case of the USA) illegal not to register a birth in many countries.

In the UK you have the 1953 Births and Deaths Registration Act requires a birth to be registered within 42 days of a child being born.

Also nice example that Google spat out here in the respect of the UK and trying to opt out not registering a birth: https://www.theguardian.com/uk-news/2019/jun/23/man-refused-...

So given that, I'd say birth certificates have in many ways and thru various avenues of law in one country or another, kinda become mandatory years ago.