Yeah, there's a huge Javascript bias. When they describe a dev with 7 to 10 years experience as: "Web Hipster; I was using AJAX before it was even called AJAX.", it's a bit like hearing nails on a chalkboard.
I think the AJAX thing is just because 7 to 10 years ago, AJAX was not called AJAX (the term was coined in 2005).
As for Javascript, it is by far the easiest to implement online, so it's good for a prototype. I don't think it's supposed to remain that way, as subscribers are allowed to choose their favorite dev area.