My primary use case of this service is for storage. I have a package and I use it to synchronize my data and to keep a backup for my device and mobile phone. I'm an IT system and infrastructure manager, and a customer of Google Drive.
I typically use Google Drive and some other tools that are included such as Google Slides, Google Docs, and Google Sheets. I mostly use it for sharing documents at work. For example, in my team, we want to share all templates on the documents we need to create. We also share pictures that we might use for marketing. Personally, I save all the documents of my project as I work on them, sometimes from home, sometimes at work, and I need to access them from everywhere. I have some projects in some folders and I save all of my documents in my Google Drive. I mainly use it for everything related to the saving and sharing of documentation.
We use it to manage our enterprise accounts. We also use it for communications like email communication, video conferencing, et cetera. With Drive specifically, we use that for storing internal confidential documents or internal documentation that require an extra level of security.