Throughout the history of Web development, we're always trying to find ways to make the user experience better while maintaining a 'works for everyone' approach. CSS had media queries which allowed us to express that this stylesheet was for print, while that one was for screen. Later, we found that we could do a lot better in servicing the user if only we could know something about that screen and thus the responsive design movement was born. Now, we find ourselves in a similar place - different user agents support different means for interacting with elements and each has potentially different implications.
Consider the humble focus ring - you see it when you are filling out a form with text boxes. It's an important visual indicator because you're about to type and you want to know where those characters are about to land. This is true regarless of the device that you are using because the only way to interact with that element is to type some text. But now