This is because the programmers are always trying new things to keep the site fresh and interesting. It keeps people coming back to see what new things there are to do on the site and with their profile. It also helps to add a personal flair to your profile when you feel as though you can change it to match your personality. They have launched both an old English setting and a British setting. So, keep your eyes peeled for further language options. For now you can try it yourself!
You just scroll all the way to the bottom of the page and click on the language, then click on "English (Upside Down)" or "English(Pirate)".