Secrets aren’t the idea. Far more than 1 million people use 6 digit pins therefore most if not all of them are shared by many people and that’s completely ok. The value is in the secret not the exclusivity. RSA private keys are compromised if someone knows the number and knows it’s part of someone else’s key, two peoples private key’s can happen to share a prime number without issue.
A sandwich on the other hand can’t happen to be eaten by 20 people without the others noticing.
Finally, what protects the company producing cokes is the trade marks on their packaging not the formula. I can know Coke’s formula or something close enough to be indistinguishable and nothing changes for them because I can’t undercut them and sell an identical product.