Why might the auditor do an account analysis and vouch selected transactions in income statement accounts such as legal expense, travel and entertainment, and other income/expenses?

The auditor conducts a detailed analysis and vouches the transactions in legal expense, travel and entertainment, and other income/expense accounts because these are accounts that are not directly affected by an accounting process, accounts which contain sensitive information or unusual transactions, or accounts for which detailed information is needed for the tax return or other schedules included with the financial statements.