Sure, XHTML is not useful on the net, etc. -- but what we are discussing here is how a correct XHTML 1.1 template should look, regardless of what the real-life treatment of XHTML for content sent over http is.
If we wanted to cater to the real-life situation, we should really just remove the XHTML support -- but a lot of people do want to use XHTML, and some may actually do it in an environment where it makes sense. For example some produce HTML 4 from their XHTML pages, which has the advantage that they can use the full XML tool suite with their content (when in the states prior to the final publishing step).
If I'm developing content for mobile phones then I do want real XHTML, some phones don't like HTML and some phones render differently between text/html and XML+XHTML.
Regards
Scott