What's the point of teaching 12 Nidanas?

In my personal practice, I've come to see that the inner voice craving for external things can be acknowledged and contemplated on, and ultimately stilled. The result is that entanglement with the external world is minimized. I'm trying to be more mindful of this internal voice, and I'm trying to improve my contemplation, so I try to understand more things in Buddhism. One thing I do not understand, is the big importance attributed to dependent origination and the 12 Nidanas. I do not understand why the Buddha goes into such depth explaining sense organs and sense objects and contact, and the like. Contact of cocaine with nose causes a sensation that you can come to crave, thus resulting in suffering. I'd also say that I was relatively clear on things being interdependent. You get good grades if and only if you study well. Hoping someone can give me a hint to how I could gain any value from the 12 Nidanas.