To understand the search volume, you have to understand the platform. Google Docs (and its companion, Google Drive) has become an unofficial haven for file sharing. Unlike torrent sites, which are publicly tracked and easily blocked by ISPs, a Google Drive link shared via Reddit, Discord, or Twitter feels "safe" to the average user.
Quite a lot, actually. Here is the anatomy of a typical "movie on Google Docs" scam. fast and furious 7 google docs