To arrive at the line 7 amount, which will be used later on the work sheet.
The line 7 amount is taxable income with qualified dividends (QD) (and Long term capital gains, if any) backed out. It identifies the amount to be taxed at ordinary income rates.
The QD is included in taxable income ( TI). It needs to be backed out, so it can be taxed at long term capital gain rates.