I think it's a matter of personal taste. Since all the examples used to display the bar, people probably had a tendency to include the black-bar without thinking too much about it. However, nothing prevents you from building a very functional site without it (I know i have).

Either way, huge prop for the awesome work! The new doc is simply excellent and the whole framework is just remarkable, particularly if one considers how far you guys have pushed it in less than a year.