Does that mean that if your quality score isn't high enough, Google will pocket your adwords money and never actually show your ads? That sounds incredibly dishonest.
Google charges you only when someone clicks on your ad. So you don't get charged for your ad showing unless someone clicks on it. The way it all started out was to show good quality ads to people. Just like search results the idea is to make ads also as relevant as possible to the user. Not defending Google, just stating facts. Some changes they have made recently (enhanced campaigns) may not be as advertiser friendly as promoted.