Crypto exchanges need sophisticated hot/cold wallet management for security. Hot storage is their equivalent to cash on hand. Hot storage can be quickly deplete

Crypto exchanges need sophisticated hot/cold wallet management for security. Hot storage is their equivalent to cash on hand. Hot storage can be quickly depleted. If a crypto exchange just disables withdrawals of one asset, users technically still can sell it for BTC, ETH or another stablecoin and withdraw that. Sometimes my banking website is down for maintenance.