Under GAAP, why are companies required to provide classified income statements

They are considered classified so that you can give them a better meaning as to what you really want to convey to others.
There are quite a number of accounts that fall under this category, by classifying these
Accounts you can obtain a better meaning.
I am referring to:
1) Financial Expenses.
2) Selling Expenses.
3) Administration Expenses.
These sub-totals have definite meanings.