The typesetting and webdesign industry has apparently been using the 'lorem ipsum' text for a while to provide a dummy text in order to test print and layout.
Aside from the fact that the text is a cut off section of Cicero's de finibus bonorum et malorum, it also fails in one huge aspect, namely globalisation.
The text is Latin, latin is the simplest of all characters we have available to us on the world-wide web. If your website is English only then, yes, you are quite done. However for a lot of us we also have to support languages other than English, the easiest of which are Latin-derived scripts.
Latin, and subsequently English, are both written left-to-right. Hebrew and Arabic, to take two prime examples, are written right-to-left (leaving numerals aside for the moment). Of course, this is very important to also test since it means a lot of change is needed for your lay out.
Especially when testing your design for sites that need to display multiple languages on the same page it is pertinent to test with multilingual text. One of the things that should quickly become clear is whether or not a sufficient encoding has been chosen.