 <p>For easy bookmarking probably. Specifying the language information in the URL is 1 way to indicate that you want to view in that particular language, ignoring your current locale.</p> <p>Wrapping this information in the URL is better than using a cookie for example, as some users may delete all cookies after each browsing session. And because of this pseudo REST like URL, /en/, it is easily bookmarkable, and search engine friendly</p>