You ask, "Why do we still have referrers?", but then you answer your question: "as a web developer, it's useful to be able to see where people came from."

You are of course correct that we don't have a "right" to this information. But I've discovered, many times, through the referrers in my logs, links to my pages from some very interesting places that I might not have discovered otherwise (because the link information that Google discloses is woefully incomplete).

Any user who wants to hide referrer information can easily to do in a variety of ways. For example, I wrote a bookmarklet that does this for you: http://lee-phillips.org/norefBookmarklet/