Node is a popular technology that seems to be taking the web industry by storm, and there are definitely some benefits. So why wouldn't a web developer be interested? I'm glad you asked. Time to get controversial, folks.
Node JS has only been around for about 9 years. I know this may sound like a lot, but it really isn't. And even if it was, the platform didn't explode upon inception. It took several years before Node really took off in popularity. So largely, this means the platform is untested when it comes to withstanding the test of time. I don't think it's too unreasonable to consider Node a 'fad' technology. That's not to say that it's bad, just that we don't have enough time to really collect an efficient amount of data to appropriately judge whether or not it's going to be as great as all the fanboys think. What we can do, however, is look at other technologies that are similar.
Ruby on Rails
This is another fad technology that, while it was extremely popular for a number of years, ultimately has started to fade into obscurity. It's still a solid platform, but a number of factors have started to cause this tech to slowly drop off. Twitter was originally built on this, which lead to the infamous "Fail Whale" issues. Ultimately, Twitter had to rebuild. And when they did, they reached for a tried-and-true industry giant: Java.
This is an old language, and honestly one of my all-time favorites. Using the right additional tools, it can also be used in web development. And as a matter of fact, it has been extremely popular as well lately, despite its age. Frameworks like Django, Flask, and Pyramid enable you to write powerful websites much the way that Rails enables Ruby to do the same. But as much as I love the language, and as popular as it is, it has one too many assumptions for me to personally consider for anything web related other than maybe some daily cron jobs or something.
Now I have no way of predicting the future. For all I know, Node could be the next big thing and blow everything else out of the water. After all, and a good developer is always looking for new ways to improve their skill set, their applications, and really anything they have their name on. Even if you're not going to use a specific technology, it's never a bad idea to at the very least take a peak. You never know when you'll be exposed to a new way of organizing your code, a more efficient documentation method, or really anything that can make you a better developer.
PHP get's a bad reputation because of how forgiving it can be, which has caused a lot of bad code to go out into the world. But the language has matured so much over it's lifetime. It runs an insane amount of websites, powers an equally insane number of online platforms like WordPress or Drupal, and most importantly of all, it was literally built specifically for websites. And the best part? It requires (basically) zero set up. If you're launching a website, I highly doubt you'll find a server that doesn't have PHP already installed and ready to go. Even if you have your own VPS like Digital Ocean and you're running a fresh install of Ubuntu, it's as easy as typing "sudo apt-get install lamp-server^" and you'll be up and running in a matter of seconds. No need for template engines or additional libraries. Just upload your site and go to town.
There are other things I could say, but I don't want this blog to be too much longer than it has to be. The important take away here is that Node is a powerful platform that has some undeniable benefits, but that doesn't mean that every developer should jump ship and dive in. Learn it, sure. I've spent a little bit of time playing with it to see what it's capable of. But I just don't know that I can say with any level of confidence that Node JS is going to do anything for me that PHP can't do, even without taking into consideration all the additional work and know how required to set up and maintain the web application for the entirety of its life cycle.