Why is site-content margin on some pages visible and on otheres not?

I imported your Megamarket demo.

When I create a new page, there is a space between the content and the footer. It is caused by the margin-bottom of the CSS class site-content.
Why is this space visible on newly created pages but not on my front page?
On my front page I cannot see a white space between the page content and the footer. Please see my screencast attached.

How do I achieve that this white space will not be visible on newly created pages? I do not wish a space between the page content and the footer.