Mining creates a competitive mechanism that is equivalent to a lottery, making it extremely difficult for anyone to continuously add new transaction blocks to the blockchain. This mechanism prevents any individual from gaining the ability to freeze certain transactions, thus ensuring the neutrality of the network. This mechanism also prevents any individual from replacing a portion of the blockchain to reduce their own costs, which could be used to defraud other users. Mining makes it extremely difficult to undo a past transaction because it would require rewriting all blocks after the transaction.
