There is no good reason that I have encountered yet where I need to use it. Generally I think people try to use the tools they have at their disposal to solve a problem. I have python, and I can do most things in python. It's not always efficient, and as an example, when I first started using python, I blindly used urllib without thinking about it. The requests library has been getting momentum recently, and I found that I prefer it and that it simplifies some of what I do, but at the end of the day why would I have searched for an alternative if what I had was working?
As developers we have to value our time. In an ideal world we would learn everything there was to know about every programming language, and pick the appropriate language for each project. In reality we stop to think that a language is capable of achieving a task, and if it is, we don't look any further.
Ironically, the reason so many people use c/java/python/ruby is because so many people use c/java/python/ruby.