Mainly because the Joomla template used in the demo site is not responsive. But the actual slideshow templates are fully responsive.

One of the things we'll be doing in the coming weeks is to also upgrade our demo site to a new template so it matches all our products features.

Here you go:

demo2.joomlaworks.net

Your width/height ratio (as set in the module parameters) will also define how the slideshow resizes eventually as the screen size becomes smaller.