"Why so much violence? Why do they not sit and talk about it?"
Ashwathama as a still child unknown to the darkness residing in the humans could not help but utter such words at which any grown man would laugh at.
No sane person wants the war as they are aware of the aftermath of the bloodbath that comes with it but it can't be helped as no one trusts each other anymore as too many people already suffered from the knife in the back.
That is why war happens, Some wars for the betterment of their kingdom subjects, Some for honour, Some for revenge, Some for justice and some for lust of power.
In which most of the wars can be prevented with the talk but for the talk, both parties mutually need to have trust in which any relationships stand and grow. Lacking trust and still trying to build bridges is nothing but a fool's dream.