A burner isolates risk. You fund it with only what a given mint, airdrop claim or new protocol requires, sign whatever that app asks for, then move any proceeds out and stop using it.
This directly defuses the most common on-chain loss: an unlimited token-approval or a malicious signature granted to a site that turns hostile weeks later. The attacker gets an empty wallet.
Example: minting from an unaudited contract with a burner holding $80 caps your loss at $80 plus gas. The same signature from a wallet holding $80,000 of tokens with outstanding approvals can cost the lot.
Related: token-approval, wallet-drainer, hot-wallet