Part of the reason for poor sales of a "play once and done" game is people can just watch someone do a "Let's Play" on YouTube and experience the (in most cases) linear narrative without having to pay.
Views on a Let's play are not equal to lost sales. Most of those people wouldn't have been exposed to the game in the first place and plenty of viewers go on to buy the game after watching a let's play anyways, even for linear story experiences. It's practically impossible to come up with an exact figure of how many sales a let's play drives, vs. how many it prevents, but for many games exposure through YouTube has gotten the word out to an audience many times larger than what a developer with a small marketing budget could have managed otherwise.
