Content Compression Content List - Exclude .*\.html ?

I was reading about Content Compression in the LTM config guide, and came across this paragraph:

 

 

 

Using the BIG-IP system HTTP compression feature, you can include or exclude certain types of URIs or files that you specify. Exclusion is useful because some URI or file types might already be compressed. Using CPU resources to compress already-compressed data is not recommended because the cost of compressing the data usually outweighs the benefits. Examples of regular expressions that you might want to specify for exclusion are .*\.pdf, .*\.gif, or .*\.html.

 

 

 

Why would F5 recommend we exclude text-based HTML from compression?