I'm speculating, but...Barrier to entry? If you're not familiar with the UNIX stack then getting up to speed on that just to play with node might not seem like a great idea (especially if you don't have a lot of spare time) or lack of applicability? It can often be really frustrating to get up to speed on something you know you're never going to be allowed to use in your current job. Some places are MS-or-the-highway shops...