Valve has promised to never put advertisements on Steam

The only things you see advertised on Steam is video games, all of which are available on Steam. Unlike console-based services like PlayStation Network and Xbox Live, there’s no sponsored content or third-party advertisements on Steam, and although Valve has admitted that it’s considered adding them, it decided long-ago that it wouldn’t be a good idea, on the grounds that it does nothing to benefit consumers. 

You may have noticed that unlike Xbox Live or PSN, Steam doesn’t have any ads. All links on all Steam pages lead to content you can buy within the client, leaving no place for sponsored content. As you’d expect, Valve has considered the option, but ultimately didn’t decide to implement it. “We don’t see a case for that ever getting user value,” Valve’s Erik Johnson told Gamespot. Johnson said that an advertisement for say, Doritos, wouldn’t work. “I don’t think anybody buys Doritos as a result of that,” said Johnson. According to Valve, this move would not work as a long-term relationship, and would in fact create “negative value” for the consumer. “It would be a bad business decision, let alone just dumb,” he added. Valve’s Robin Walker reiterated, saying, “Ads don’t serve any value to costumers.”