Probably this also have to do with the quality of the enginner.. im sure companies have a hard time trying to hire C/C++ class of enginners (and java at some extent).

Im sure nature+culture+education also have a hard time to produce this sort of profile.. so the market have to fit, to get its work done (spending more in hardware to compensate maybe?)..

But as a contradictory example, see facebook.. started with the easy (and spaguetti) PHP.. and now that things get really complicated.. they have to turn out to C++

You dont see this sort of infrastructure problem on google, that has started with c++ right away..

And also twitter, started with ruby, and ended on Scala (im sure it cost a lot to buy the ammount of memory JVM requires, but is pretty fast)

But of course, the majority of jobs come from mid to small sized shops.. (and startups) that like their precedents before them.. are starting the easy and productive way.. with things like node.js .. nothing against that , but if they get really big as the examples i´ve gave, they will start to feel the heat :)