Data protection. An employer would breach confidentiality and therefore be liable
So how do they get away with: “Here I will hear it from the horse’s mouth now, exactly how much the player’s earning at that club and I can say, ‘Yes we can go to that,’ or ‘No we can’t go to that'"? Genuine question by the way, not being an arse! It's just that if it is confidential he's a bit daft admitting that they all discuss it! Is it not the case that there's a legitimate reason for needing to know the amount (because the club would be effectively taking on the contract) which means it can be mentioned?