Why Do Older Contracts Still Need to Be Audited for Integer Vulnerabilities?

Older smart contracts written before Solidity version 0.8.0, or those that explicitly use unchecked blocks, still need to be rigorously audited for integer vulnerabilities. These contracts do not benefit from the compiler's automatic safety checks.

Auditors must specifically look for the correct and consistent use of SafeMath or manually verify that every arithmetic operation cannot lead to an overflow or underflow, as these flaws can still be exploited to manipulate balances and drain funds.