How do I explain why Styles are important to a non-user?

You will run into this question and issue with the project engineers, principals, and many others.

Most use Excel.
They use Excel templates.
They keep reusing and probably tweaking them a little from job to job – at least I hope so.
That is what the Framework product is for AutoCAD Civil 3D - a working set to templates.

Even if all the people do is look at reports from the accounting/finance department you can explain the Framework for Civil 3D this way:

"You would not want to create a new report every time you needed to see an Income Statement or a Job Costing report would you?

Styles inside of Civil 3D templates do the same thing in AutoCAD Civil 3D.

Styles are really just a way of reporting what’s in there only instead of pages of numbers you get drawings with annotation.
There are lots of kinds of things to report on and lots of detail available for reporting…
so you need numbers of styles that report the “suitable” data at the right time and also look good on the page.

Someone has to do that work. Production ready Styles are not supplied with AutoCAD Civil 3D.

The Framework for Civil 3D has all the right stuff."

It is a Better Place to Start.