Bingo. Some of these kickstarted games may make massive profits; others may make the game, and then fail to sell many boxed copies because there's no market. Then they've essentially broken even.
That may be a success in their eyes - they got to make a new game, and the backers got a copy - but breaking even isn't "showing publishers what's what."
And arguably it isn't. There's little doubt there's money in it, but not enough money to make it worth a large publisher's time.