Configuring infrastructure by hand can be a tedious and error-prone process. By automating it, you remove the potential variability of a manual implementation: computers are good at boring, repetitive tasks, so use them for it!

Once automated, the labor cost of provisioning more resources is effectively zero—you have already done the work. Whether you need to spin up one server or a thousand, it requires no additional work.

From a practical perspective, resources in AWS are effectively unconstrained. If you are willing to pay for it, AWS will let you use it.