Dhiraj ur answer is convincing. Profit & Loss A/c. is a statement recording Incomes and Losses / Expenses.
To assert my point further, consider the accounts of Professionals where it is called "Income & Expenditure A/c." Even in that case we have either Excess of Income over Expenditure or vice versa as the end result, but not both.
Therefore the word "and" is used in Profit & Loss A/c. to signify both Incomes and Expenses.
Argument put up by Sneha about consistency is also acceptable.
BUT I must say........such good arguments may not also click when facing an interview. Hope this discussion can help someone in future.