It's a bit more than a box ticking exercise for the banks. It is a legal requirement and if they are found to be in breach of the law there are serious ramifications for the bank and potentially the staff involved. The government agencies that oversee the AML/CTF/KYC legislation are unable to offer much, if any, leeway when it comes to breaches.
The fact that you were asked for the birth certificate years after the account was opened, due to an error made by the bank at the time the account was opened, was probably the result of an audit by the bank. The fact that the error was made years ago does not offer up reason to continue with the error once discovered. The bank probably should have offered a few more options on how you could rectify the situation rather than just telling you to go into a branch with the document.
Back in the day before KYC was taken seriously, banks had accounts in the names of Mickey and Minnie Mouse, the neighbours pet cat and dog and any other thing you could think of as means for hiding money and money laundering.
The last thing any of us need are banks getting lazy on KYC/AML/CTF and the regulators letting everything pass them by and not caring.