Google Drive wants to be your universal cloud drive, meaning it wants to house all of your files. Just keeping them in the cloud is not enough, making it possible to use the in the cloud is more important.
Which is why Google already has a number of editors or at least viewers for quite a few file types.
But it can't possibly support them all, especially now that the desktop app is available, people put everything they have on their computer in that folder without thinking of whether Google Drive "knows" what it is or not.
It gets even more complicated when you add third-party apps into the mix, especially if they use custom file formats or types.
This is where a new Google Drive SDK feature comes in handy, developers can now provide thumbnails for the files they sync to Google Drive, so users will be able to know at a glance what that file is.
"The new thumbnail property on the File resource includes two sub-properties that you can set when uploading a new file or updating an existing one: “image” to contain the base64-encoded image data and “mimeType” to specify one of the supported image formats: “image/png”, “image/gif”, or “image/jpeg”," Google's Claudio Cherubino explains.