Couple of things, actually.
Node.j lacks enterprise tools and solutions. Most of Java based systems we see, are using IBM tools one way or the other. And it is a norm in enterprise scenario. But lack of tools and support from major vendors for Nodejs mean, it is considered as a risky proposition to even pick from client side! When a team of people discuss about infrastructure and feasibility, there are lot of factors like, will this language got enough enterprise tools for us to use? Can we get enough resource in this lang? Node.js is buzzword, but there are very limited experienced resource simply because it is pretty new to the market.
Corporates want some big names that used certain language to assure themself that the choice they made is right one. Trust me, even names like LinkedIn and twitter weren't enough to convince the higher ups to go with Node.js for simple utility module. Unless Node.js get some tremendous support, tools to go with enterprise system, it will never become mainstream language in an enterprise setup like say, Java!