When you think about it, a lot of marketing is pretty simple. The concepts aren't overly complicated, but that doesn't mean doing it is easy.
Simple and easy are two different things!
For example, most people know they could be doing more or better things online. Maybe you've thought of investing more time and resources in LinkedIn but still haven't done it.
Sharing and interacting with people regularly on LinkedIn is a simple concept, but it's not easy!