Because then the site would not demonstrate the pain caused by poor RTL support, as most of its target audience will not be able to make sense of the script.

The point is that even when you understand the script and the language, you find yourself looking at a website with messed up formatting, punctuation in the wrong place, and broken sentences when BiDi gets involved. Those of us who deal with this all the time are used to it, but most people have no idea how broken things are.