As said, i am not really that knowledgable in the whole blockchain topic, so anyone feel free to correct me where i am wrong:

• Why should i trust those parents/friends (or doctors if present)? Presumably this would be a global system? So why should i trust a group of random people from idk Somalia? I probably don't even fully trust any institutions there. My understanding (simplyfied) is that with bitcoin the coins themself are mined by finding solutions to hard math problems that once found can be easily verified by anyone. So at the base you have something i myself can verify to be true. Whoever finds the right number first gets the coin and after that you only need to keep track of trades and this is where the blockchain helps.

• What data would be stored on this block chain? Honestly seems like a bit of a privacy nightmare. I wouldn't want all family history and identifiable information to be public, so it can serve as an ID.

• To go along with the point above, how would you verify that a specific certificate on the chain belongs to you? Similar to a password for a crypto wallet? So that it can be lost without ability to be recovered, that your parents have control over it from the start, and that people who gain access to it can abuse it? Basically all issues similar to the US social security number? Or by having a passport or similar do the job, which kind of defeats a lot of the purpose of that blockchain being the source of ID.

• It wouldn't be enough to make a birth/death certificate. You would still need a system to change/add information. Like what if somebody changes their names? Also not every child will be added from the start, so you will need to handle late additions (that e.g. make date of birth even more unsure). What if someone goes missing or dies and it isn't reported? Also a small number of people might also require new identities for security purposes (think victims of abuse), how do you handle the need for an institution having the ability to create such fictional new identities?

I could probably find more issues.

So imo truth ultimately has to come from somewhere in the real world. And at places that might benefit from some system that is seperated from institutions (because they are poor, authoritarian, oppressive or have unstable governments for example) will at the same time have more difficulties providing something you can trust.

And in reverse regions that might have an easier time like the EU don't really seem to need it. Also as far as electronic IDs go the EU is planning that with eIDAS 2.0 and the EUID. Don't think it invloves a blockchain at any stage.