Personally, I'm not against Cancel buttons in some cases for the simple reason that I'm not sure the site will work fine with the Back button on multi-page form

Personally, I'm not against Cancel buttons in some cases for the simple reason that I'm not sure the site will work fine with the Back button on multi-page forms that are used for almost all payment transactions. I also tend to use a Cancel button if there's one, or a navigation link to exit the process because I'll be sure to avoid a "resubmit POST values?" alert if I were to click 'Back'.