"Maximize the ratio of content to markup" What's the underlying principle?

Hi Folks,

Yesterday I read this:

"Search engines look for semantic markup with a high ratio of content
to code." [Building Findable Websites by Aarron Walter]

For example, this is not good design:

<div>
    <div id="Main">
        <p>Hello World</p>
    </div>
</div>

The outer div is providing no benefit.  It can be more simply expressed
as:

<div id="Main">
    <p>Hello World</p>
</div>

The later version provides a higher ratio of content to code (tags).
And from the quote above, search engines rank higher documents with a
higher ratio of content to code.

What is the underlying principle?  Why do search engines prefer
documents with a higher ratio of content to markup?

Can the principle be applied to XML data design?

For example,

This is not good design:

<Author>
    <Name>Paul McCartney</Name>
</Author>

The Name element is providing no benefit.  It can be more simply
expressed as:

<Author>Paul McCartney</Author>

The later version provides a higher ratio of content to code (tags).

What do you think?  Is there a principle of data design being
illustrated here?  Can you articulate the principle?

/Roger