They increase revenue by...getting customers. Therefore everything on the site is for the customer, in terms of acquiring them.
If I go to your restaurant's website and have to dig to find the menu and the page is just plastered with "Fine dining with a wonderful view" and pictures of models eating... that's not helping me, that's advertising to me. And now your website is no longer a utility/service, it is a billboard. The only reason I tolerate the billboard is because of the utility, and if the utility doesnt exist, why would I ever come back.