What Does Neuroscience Add to Behavior?

I loved that conversation with Malcolm Gladwell about rooting for the underdog. He was really focused on what happens when you lose, not if you win. But winning for the favorite is like no big deal. This is what their brain and everyone else's brain expects. And if the underdog wins, it's like, boi, dopamine surprise. I'm curious about the value of describing in terms of underlying neurological tendencies as opposed to the more familiar personality patterns. Why do we need the neurotransmitters?