I am sure if you can build a working time machine, you are capable of going back to 1920 and stealing a few chickens/cows/pigs/sheep with nobody spotting you.
Even going back to dinosaur times has risks, as Ray Bradbury showed that going back in time to kill dinosaurs can strawberry float time up if you even step on a bug.
And if the future is so shitty, would they really care about interfering with history? We strawberry floated up so bad that there is no meat left, interfering might improve things.
God I am bored today. I need to go to the pub.