TL;DR: MEV exists because of four fundamental properties of blockchain architecture: public mempools that expose pending transactions before execution, block producer discretion over transaction ordering, DeFi protocols that continuously generate economic opportunities through price discrepancies and liquidation thresholds, and atomic execution guarantees that allow complex multi-step strategies to either fully succeed or fully revert with no risk of partial failure. These structural features combine to create an environment where informed actors can extract value from transaction ordering. MEV is not a bug in any single protocol. It is an emergent consequence of how blockchains process financial transactions in a transparent, programmable environment.
간단한 설명
To understand why MEV exists, you need to understand the unique combination of properties that blockchains offer to anyone willing to exploit them. No traditional financial system has all of these properties simultaneously, which is why MEV is a phenomenon specific to blockchain.
In traditional finance, order books are not public before execution. A stock exchange does not broadcast everyone's pending orders to the entire market before matching them. Market makers and high-frequency traders have information advantages, but the raw pending order flow is not universally visible. On a blockchain, every pending transaction sits in the public mempool, fully visible to anyone monitoring the network. A user's intent to swap $500,000 of ETH for USDC on Uniswap is broadcast to the world before it is executed. Any participant with the technical capability to monitor the mempool can see this transaction and react to it.
This transparency is a core design feature of blockchains, not a flaw. Decentralized networks need public transaction propagation so that validators across the world can receive, verify, and include transactions. But the same transparency that enables trustless verification also enables informed front-running by sophisticated actors.