How is that dronabinol is legal but marijuana itself is not?

Starting to change. There are a number of states that allow medical marijuana, and there are now two states (colorado and washington) where recreational use is legal (still waiting to see how this is going to all work out given it is still illegal from a federal law standpoint).
Our laws. I agree with you - it makes no sense. That's due to the laws passed by our national leaders in washington.