Requiring a dedicated tool to even see the code, Visual Studio for example, is very limiting.  Not to mention that unless you can read binary you have no idea if the source code you're looking at is actually what is running.  

That's not to say huge applications should be built in powershell but for basic scripting tasks like file maintenance or simple web service calls it's a very powerful tool that trying to do in C# would be more trouble and ad no benefit.