The problem with blockchain transactions on Ethereum, Polygon, and similar chains is that the user will need to pay for gas. To pay for gas, a wallet needs MATIC/ETH. To get MATIC/ETH to pay for gas, a user might get it from an exchange, a friend, or themselves, maybe from a wallet that is already connected to their identity. A malicious actor can find out where their MATIC came from and link it with the user’s identity. Relayers help solve this problem.