During Game of Thrones S07E04 we saw a battle take place during the last 10 minutes of the show.
During this battle we see Dany flying around burning everything. I do understand it is not good TV to have her kill everyone in one pass (she could have flown over the line formed and burned them all at once) but that's beside the point. The bigger issue is, she complained they lost all their food in the attack the Lannisters did. Not only did she kill the army, she also made it a point to purposely fly over the caravans and burn them too instead of letting those be for spoils of war.
There was no point to purposely burning the food. The Lannisters were clearly outnumbered and were easily killed with nowhere to run. They had no way of sneaking out any of the food either. She could have left them alone to bring them back since the Dothraki were mounted. Attaching them to a few horses who lost their masters wouldn't be that big of a deal.
So why did she do it when it was something she even stated they needed?