Because if you want to change any part of your document, all you have to do is update the style and the document is changed automatically. For example, if can change Heading 1 to a larger size, different color, and font family, every Heading 1 gets updated immediately.
The alternative is to change every heading by hand.
Believe it or not, I often receive documents that use the Normal style for everything. Chapter headers, bullet lists, comments, and the paragraph text – all use the Normal style. Updating the document takes forever.
So, how can you update the document with just one click?
Select the style you want to change. Let’s say Normal.
Go to Format, Styles and Formatting.
In the Formatting of selected text box, click on Normal.
Click Select All. A drop-down arrow appears in the right-hand corner.
Click on the arrow and select Modify.