Why automate IT infrastructure? Actually, automating is not the best solution only for IT infrastructure, but for many things in software development. And why?
Manual processes are slow, highly vulnerable to human failure, not scalable, hard to create, update and keep a standard, etc. I could cite many other reasons for anyone to run away from any manual processes. They are the opposite that is proposed in agile methodologies or DevOps culture. Now specifically about infrastructure, we can affirm that without automating it's impossible to get the best of the resources of any Cloud service. We can see the why in the next lines.