Not sure how this is somehow unique to Google. Amazon, for instance, has both "Amazon Cloud Storage" and "Amazon S3".
Maybe you're using the term "same thing" too broadly.
Google Drive is about allowing non-developers to store files via a built-in interface. You can sync files automatically between computers and view and edit the files online with various web services.
Google Cloud Storage is about allowing DEVELOPERS to store files on behalf of their customers to be able to build applications that need lots of storage but without the developer needing to provide their own storage infrastructure.
It's like the difference between Microsoft Office and Microsoft Visual Studio. With one, a user can USE office-like applications on a Windows machine. With the other, a developer can CREATE office-like applications to run on a Windows machine.
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