Everybody says they ignore banner ads, but it's still one of the most common forms of digital advertising, because it works, even if people don't realize it. Sites that have high user engagement and trust in the site have high conversion rates. This is one way of demonstrating that engagement and trust.
Also, it's attractive not just for banner ads, but also for potential formal site sponsors (e.g. sponsored posts, etc.). While you might not click on a banner ad for Johnson & Johnson products, you might be more likely to click to a website for a sponsored post, especially if there are responses saying they've tried the product. Robbie McCombs' sponsored post for his basketball season preview a few weeks ago, and the Deseret News' sponsored post for their 1984 commemorative edition magazine are examples.
And honestly, high user engagement is a big strength of CougarBoard's. People spend time here. There's a community. Most websites couldn't say that the majority of users have made a purchasing decision because of the website.