They are available should you create any kind of form, whether with Contact form 7, or any other plugin that allows you to create forms. Basically you would use the form element classes and structures in your own, but I noticed I did not provide all the classes, except the buttons and a couple others. For example, the checkboxes would have a structure and class like this per checkbox:
For buttons, text, links, etc., you would do this:
The other btn classes can be used to adjust the sizing from big to small: btn-large, btn, btn-small, btn-mini
The form fields like text, textarea, and select are automatically styled when you add them to your form or page.