Hi EdBiancarelli,
That is also the right way actually to define variables in ...

Hi EdBiancarelli,

That is also the right way actually to define variables in hook_install, But by using default parameter of variable_get("xyz",$default); We are actually reducing some number of lines.

In your case also, Even if user has not configured the page, then default parameter will come into picture.

Both the ways are correct but that method just reduces some number of lines (Thats what i think). Even i got to learn about this a week ago. Check point number 2 in https://www.drupal.org/node/2452803#comment-9746245