We're busy people; we don't have time to figure things out. If we can't find what we're looking for in a few easy clicks, or a few quick minutes, we'll move on and try to find it someplace else.
Remember, if your visitor doesn't figure it out, you've wasted an opportunity, and if you paid good money to drive that person to your site, you wasted your money. Just because they showed up means nothing unless you're making money.
Sites that make it really clear what you're supposed to do are the most effective. A big "Start Here" and a simple 1, 2, 3 series of forms that don't confuse and don't frustrate are obviously preferable to a website that some programmer said, "They'll figure it out..."
And that's because most people won't figure it out.
A quick primer on web ad models
There are three basic advertising models on the web:
You are ultimately looking at your final cost per action which means you need to know what that action is. If your website makes money from selling a product or service, that action is a purchase. If you're selling advertising on your site, then you need to get that visitor to look at as many pages as possible and, preferably, click on those ads.
The trick is to balance the model you're paying for traffic against your acceptable cost. So, if one advertising source has a really high conversion rate (everyone who clicks buys) you might want to pay on a per click model. Alternatively, if you get really high click through, maybe pay on an impression model.
But you have to watch and learn and adapt as you implement your plan. You need to modify your advertising to drive more qualified traffic and you need to modify your site to maximize the return on that traffic.