The concert organizer acts is an inherent central authority. The whole problem is easily solvable with a QR code and a web API.

Using a trust-no-one arctic-melting decentralised layer on top of a thing that is inherently decided by a single real-world entity makes no sense whatsoever.

I think that the true value of NFTs will come from interoperability, where there is no central authority, and you can treat it as a sort of cross-platform standard for verifying ownership of digital assets. This doesn't really apply to concert tickets (except if someone grants some special privileges to people who went to a certain concert in some unrelated virtual space), but there are advantages to not centralising authority for certain things (say, domain name ownership, why should ICAAN control that).

What stops me from copying ticket data from the NFT and using it to enter the concert?

If the concert venue somehow checks ownership of private key associated with the NFT it means they are effectively using some form of identity verification and blockchain is really really bad for this purpose

You don't use the blockchain to verify ownership of a private key. You know the public key, and the owner of the private key can sign any message to prove that they indeed have the private key associated with that public key. This can be done completely offline.

Isn't a crypto wallet, literally a key pair, the purest form of identity verification? It's something you have (private key) and something you know (passphrase). No need for some central authority, no need for privacy concerns.

You are right on the latter point, a keypair itself is a pretty good method to verify pseudonymous identity.

However, we are talking about NFTs as tickets. Traditional ticketing relies on secrecy, or in other words possession of ticked-id grants entry. Data embedded in NFTs is (and has to be) public, therefore token auth model does not work, you must use challenge-response model. The very point here is that ticket data has to be linked with a keypair and provided at the moment of sale to be verified upon entry. Public key must be provided at moment of sale, blockchains are one way to store that link, private database of ticketing system is another. Blockchains bring their own disadvantages and the only advantage is trustless transfer.

In what scenario trustless pseudonymous transfer of a ticket is an advantage worth disadvantages of the blockchain.

What's the benefit of making those resellable? To encourage scalping?

NFTs can be created that are non-resellable, you just build that into the smart contract. Even if they were, you can see the full transaction history and decide to reject anyone but first owners