Why didn't all of this happen within Terraform? Why keep a separate playbook for deployment?

Although Terraform is excellent for describing and managing infrastructure as code, it does not always cover all aspects of application or system configuration and setup.

Playbook (e.g., Ansible) is used separately for more detailed and flexible configuration, package installation, configuration file management, service startup, and script execution, which are difficult or inconvenient to do with Terraform.

Separation of responsibilities:

• Terraform is responsible for creating and modifying infrastructure (virtual machines, networks, load balancers, etc.).
• Playbook handles the configuration of already created resources, ensuring the desired state of software and services.

This approach increases modularity, simplifies maintenance, and allows the use of the best tools for each task.