I'm so busy typing and revising documents. I know how to change the font and size and to use Bold and Italic. That's all I need most of the time. Styles are for complex formatting I don't need any complicated formatting, so I don't need to use Styles. All these reasons are bogus.
Styles can be very easy to use.
Using styles can save you time. Take a little time to get used to them and it will pay you back many times over. Styles aren't just for complex formatting. You can use them effectively in your everyday documents. If you use styles while you are writing your document you don't have to go back and apply the formatting later or pass the document on to someone else to apply the formatting.