I've bought more games in the last 5 years off seeing them in streams than from any other review or advertisement because even if the streamer is a paid shill, there's only so much bad design that can be hidden in live play that makes it easier to see what I'm in for. I can understand having an unrealistic opinion of your story quality and not wanting to spoil it for potential new audience, but at the same time I think they're underestimating the number of people that would still buy a game even if they see the story through on a stream. Beyond that, they could be getting fans that, while they don't buy one particular game because they see it streamed, they had a good enough time watching it that now they have that company name in their heads, it's free real estate for a future release to be considered as a must buy so they can get on the wagon too.