Is it especially true in the armed services? I have a friend who was in the Army during Vietnam (cryptology, not combat); he took to demanding copies of his immunization records after he got a second tetanus shot months after he'd had one because the records weren't there.
The VA is a notoriously poor record keeper. Nothing is computerized and records are just kept in huge wherehouses. Once the records are pulled for any reason, they may never be seen again.