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.