There are "systems developers" and there are "applications developers". The two groups often use different tools, so JavaScript vs CoffeeScript isn't much more

There are "systems developers" and there are "applications developers". The two groups often use different tools, so JavaScript vs CoffeeScript isn't much more surprising than C vs C++ or Win32/COM vs .NET for that matter. Systems developers provide services for other developers; generally they want to minimize dependencies. It doesn't make sense to write foundational tools in CoffeeScript unless all the clients of those tools will be written in CoffeeScript as well. Otherwise you're just adding complexity to their projects and making them harder to debug.