The screen space on a mobile device is smaller than a desktop. Touch is the primary mode of input. Entering data into forms is painful at best when you're trying to tap it out on a virtual keyboard with small keys. That makes the user interaction different than on a desktop.
Make it easier for users to interact with your site on a smartphone. Simple things like using a font size that is legible on small screens, or making it possible for them to call you with a single click, go a long way towards improving user experience.