because you get the content streamed from a server afaik (i'm not that deep into all this so take it with a grain of salt) and that really rubs ppl the wrong way because pirate site etc.
I think the bigger issue with regards to streaming stuff to people's computers is that it usually requires bypassing antiviral software in order to work. Still, devs choice, peeps don't have to play the game...
Still, as much as I'm kind of indifferent to the dev's primary game, gotta love the games that parody streaming sites. Do more of those!