Not that unique anymore. At this point it is called Steam sales, Humble Bundles, Prime and what not.
Pretty sure I have hundreds of games I have not played.
I will totally get to them some day! 
Heck, the majority of people who do play games they buy, still dont get through the campaign of those games.
70% of people who bought D4 on Steam have not reached lvl 50, nor finished the campaign.