The jQuery Mobile form elements that are used in the MVC Mobile Application were designed to be a flexible width. With a flexible width, they'll fit the width of any mobile device, so that labels and form elements will be presented differently based on screen width.
On a narrow page, the labels and form elements will stack with the label on top of the form element to save horizontal space:
If you're using a mobile device with a wider screen, like a tablet, then the labels and form elements will appear on the same line in a two-column format:
Dynamic form layout allows you to take advantage of the screen real estate that is available to your application, and also allows you to provide the best and most usable format for your users, depending on the mobile device in use.