Referrers are useful and can be a friendly, automatic way of letting someone know how you found their page. I've discovered many links to my pages on other websites, and whole articles discussing my articles, through referrers. Since none of the other pinging mechanisms ever gained universal traction, it's the best thing we have, and I'm sorry that it's all but disappeared. And I remember how amazed I was to discover the existence of "referrer spam" years ago.
You can block referrers in a number of ways whenever you'd like, for example with a simple bookmarklet:
http://lee-phillips.org/norefBookmarklet/
Finally, looking at search terms that led to your site can be very entertaining.