OK those POAP are on a decentralised blockchain but it seems to be a useless constraint to depend on a specific contract and their creator for this use case. It

OK those POAP are on a decentralised blockchain but it seems to be a useless constraint to depend on a specific contract and their creator for this use case. It's like doing centralization on top of decentralization. Event organisers could provide attendance proof with their own contract/address and you'd still have a proof of attendance as long as the organization is verifiably linked to the contract/transaction issuer. You then only need a database (easily shareable) of verified event organizers to be able to verify anyone event attendance history. All the fluff on top of the attendance verification mechanism provided by this company doesn't depend on the blockchain at all.