Hi, dae. You don't need macro to delete unnecessary styles.
Follow the below instruction.

1. Right-click a sheet tab, and then click "Select All Sheets" on the shortcut menu.
2. Right-click a sheet tab again, and then click "Move or Copy".
3. Select "(new book)" from the "To book:" dropdown list.
4. Check "Create a copy" box, and click OK.

The new workbook has only Excel default styles.