Why use standard design elements?

In their book "Prioritizing Web Usability" Jackob Nielsen and Hoa Loranger make a strong case for using standard design elements. Even though the book is from 2006, this issue still seems relevant. Here is an excerpt from the book that states the main points:

Seven Reasons for Standard Design Elements.

Standards ensure that users:

1. Know what features to expect

2. Know how these features will look in the interface

3. Know where to find these features on the site and on the page

4. Know how to operate each feature to achieve their goal

5. Don't need to ponder the meaning of unknown design elements

6. Don't miss important features because they overlook the design element that is not standard.

7. Don't be surprised when something doesn't work as expected