Not provably fair doesnt mean that the site is cheating, it just means you cant verify wether the site cheats you or not and it only works if you verify your own bets otherwise it doesnt.
I do know that. I also do know that not knowing whether my money was wagered fairly or not means that cynicism and skepticism should be the default. We don't automatically assume the best of others in hypotheticals, do we? That would be an incredibly silly way to operate!I doubt that majority of the player would verify their bets one by one after rolling tons with the autobet on the original stake game, do you?
We have bots for that, but regardless just because a minority of players actually care that their bets are verifiable doesn't mean that it's not important. 
Remember, I'm not complaining about Stake at all. I'm complaining about these providers. That's an important distinction.