I use Microsoft IIS because it is shipped by default with Windows Servers for which of them I usually develop applications. IIS perfectly managed from PowerShell which I use as well, thus it is very easy choice for me. I could have clean Windows instance and bring it to desired state using PowerShell capabilities. Also this is default configuration for debugging in Visual Studio which means that I develop in the environment which is closer to production.
I use PowerShell because it is a Perl for .NET. If you love Perl you will love PowerShell too. Great design decisions and power of Perl multiplied by power of .NET!
I use PowerShell because it helps me with tools, commands and possibilities to expand Windows Shell to add utilities. Teamed with scoop.io it is really helpful to bring powr to shell like we also have in nix systems