When following the certification training, they tell you what you need to know when you need to know it.
They keep it simple so that you learn in the correct order and you don't get bogged down with details, get bored and quit.
What they don't tell you is that behind the scenes (while doing the actions they recommend), there is more working in your favor than they let on.
SEO is the main focus because it equates to free traffic from Google, Bing and Yahoo!
That makes a lot of sense because in affiliate marketing it's about building up many smaller amounts (or a few big ones, or both) to build a sustainable, repeatable business that will support your dreams for the rest of your life.
You simply cannot do that with a paid advertising model to get all of your traffic.
What they hint at occasionally, but don't really dig into in the certification training, are all of the OTHER free ways that you can enhance your traffic.