system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why would I want my food to be antibiotic-free?

I'm seeing a lot of advertisements for antibiotic free chicken/beef. Antibiotics are important to humans for resisting infections and staying healthy, so why would I want the animals I eat to go without them?
gpt
Farmers really want to try to make sure their herds/flocks grow big and strong as quickly as possible.  They want their animals to stay healthy too.  So, to do that, they have for years given small doses of antibiotics to their animals to keep them from getting sick.  Food safety advocates and medical professionals are worried though that this could make humans sicker in the long run.

Antibiotics are great!  They keep us from dying from stuff like tuberculosis or staph infections.  But they don't always kill all the bad bacteria when we take them.  They basically give our immune system a huge advantage in fighting infection.  But some of the bad germs survive and become that much stronger.  The big fear is that you giving farm animals antibiotics when they don't need them, it could make some human diseases harder to treat down the line.  We already know that TB and staph have some really nasty drug resistant strains out in the wild, and we don't want more of them.

We're also not quite sure how these antibiotics given to animals that give us meat or milk might affect us.  There are lots of rumors that the antibiotics given to animals might be doing things to humans.  We're still not sure if these things are good or bad, or if they're wide spread.  Scientists are still figuring it out but some think it might be affecting how quickly people are growing or that it might be killing the good bacteria in our bodies.

Environmental activists also worry that these medicines might be getting into ground water and affecting the ecosystem.

With all these concerns, and with people wondering more and more where their food comes from, grocers have started slapping "antibiotic free!" labels on their food packaging.  It was a smart move: "organic" and "all natural" foods have become very popular and the labeling makes people feel better about what they're buying.

In the end, though, we don't really know if these farm practices are really as bad as we worry they are.  The concerns we have are very real, and very valid, but scientists need to do a lot more research into how what the farmers do affect the rest of us.  There is also very little oversight into the way food is marketed and labeled, so we don't always know if the foods labeled as "antibiotic free" are really as free of antibiotics as they claim.  Mostly, it's good marketing.  We buy the "antibiotic free" meat and milk because we feel better about ourselves when we do.

Michael Pollan's "The Omnivore's Dilemma" covers a lot of this (where our food comes from and how farm animals are raised) if you're  interested.