As the duckduckgo guy puts it: "When you search on Google, not only is your info stored, but also when you click on a link, your search terms are passed on to that site via the Referer header. A lot of sites use this information to tailor content and advertising to you specifically. Your searches also show up in analytics tools, which people use for SEO and other tracking purposes. This information leakage creates legitimate privacy concerns."
And what's to stop ISPs logging the plain text https urls you access anyway?