The 48-year-old actor, who raises six kids with fiance Angelina Jolie, believes the film represents wider changes in the world since the economic crash of 2008, reported Contactmusic.
"We live in a violent world. I certainly grew up hunting, which is a very violent act. Have you had a hamburger? The way they butcher a cow. It's barbaric. It's horrendous. This is the world we live in. I see it as absolutely important to film," Pitt said.
The actor, who plays assistant to a hitman in the Andrew Dominik-directed picture, also said he wanted to join the project because it was commenting on our time.
"We are always looking for stories that say something about our time and who we are. I certainly felt on reading the script that this was making a commentary. At the time, people were at the apex of the mortgage loan debacle, people were leaving their homes.
"I felt I was reading a gangster film and then it coalesced that this microcosm was saying something about the macro-world," he added.