No, you don't' have to if you are using Google Cloud Shell, If you intend to use the local shell, then you need to install gcloud as well as kubectl tools.
Google Cloud Shell is a shell environment for managing resources hosted on Google Cloud Platform (GCP).
Cloud Shell comes preinstalled with the gcloud and kubectl command-line tools. gcloud provides the primary command-line interface for GCP, and kubectl provides the command-line interface for running commands against Kubernetes clusters.
If you prefer using your local shell, you must install the gcloud and kubectl command-line tools in your environment.