Autocomplete isn't just a form of documentation, I very rarely use it that way (that's what go to definition or GitHub are for). I know how to override ToString(), but ov[tab]tos[tab] saves me about 40 keystrokes. Stubbing out an interface can save me hundreds.

Scott Hanselman has a great tweet chain (or blog article, can't remember) on the fact that you have a limited amount of keystrokes in your life. I'd rather not waste them on something a machine could do.