I don't see any real usefulness of that function...
Why should I renounce owning my contract?
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It's a matter of trust.
If the contract's owner has special access to the contract, it's a security risk. Depending on the contract, the owner may do malicious acts in the contract. In the worst case, the owner can possibly even rug pull the contract and basically steal all user assets.
If you renounce ownership, it means nobody has special access rights in the contract anymore (unless there is some extra access stuff coded). Therefore, since everyone has the same access, there is no single point of failure and no trust issues.