What are the benefits of using build scripts (Ant, Gradle, etc) over writing the scripts in a programming/scripting language?

A long time ago I used Ant to build a C# project (a Unity3D project, to be precise), but I slowly switched to doing most of the logic in C# itself. Now it's entirely in C#. I found a lot of benefits by doing this. Off the top of my head: I can write...