"Can I help you?" is a default question. It's a wall we are trained to put up when we want to give the impression of helpfulness (e.g. retail sales people). Seth Godin wrote a great post on defaults, which you can read at http://sethgodin.typepad.com/seths_blog/2008/10/rethinking-defa.html
Think about the last time you asked or were asked "can I help you?" I bet the response was "no." That's a default response to a default question.
What if, in a retail setting, you were asked, "what are you looking for today?" Your response could be equally dismissive (e.g. "nothing, just killing time") or the sales person could uncover a hidden want (e.g. "I want to replace my pair of Rockport dress shoes").
Do you ask default questions or do you ask "discover" questions that uncover hidden needs that make you more valuable as a colleague or supplier (e.g. your co-worker is clueless with Excel, your client has a big event coming up)? Who do you think has more value in the eyes of colleagues and clients?