Sure, it seems to be working. That doesn't mean developers should be complacent. You shouldn't settle with an owner doing something that's in their best interest but charging more for it. Stopping piracy and promoting games gets Valve more money. They aren't doing it out of kindness. Just as they're doing what's in their best interest, devs should be too. They should be trying to get that 30% knocked down.
Valve is doing a lot of good stuff right now, but accepting them as some kind of hero is how you get fucked over. Don't be complacent. They're a capitalist company trying to make as much money as they can. As long as their goals align with the consumer it feels great, but don't think it always will.