Because as the other answers to the question show, sometimes there's more to be gleaned from a human interaction than a straight fact-finding trip to the Internet.

Or, sometimes, people just want to interact with a human. You know, converse. We're a peer group, right? We're here to discuss things. Op is discussing. If the entire group deemed it too obvious a question to merit replying, no-one would have replied.

Further, this question and answer is now available to Google to crawl, store, and return for future searchers. How did Google get all the answers that are available in the first place? Someone typed a question, and someone else answered it.

Finally, I Googled _your_ question and came up with this answer:

"Because receiving a personalized response is far more gratifying than reading a Wikipedia page. It makes you feel at the very least a connection to another human being which other than " leaving a footprint " is mans greatest desire in life."