Direct advertising sales can be a huge opportunity for established websites to increase their revenue. Direct advertising is great for bloggers and smaller websites because you are not required to deal with an intermediary – you keep every cent you make.
Think about it this way. If you sell a banner through an ad network and that banner is worth $40 per month, you will get less than its true value because the ad network has to take their cut. If there are people willing to pay $40 for ad space why should you sell it for less? There is no reason why you’d have to share the profits with a middleman, that is, if you can find advertisers on your own.