Because I care about what I put in my body. I buy from known, well-regarded, local sources.
I generally don't buy produce in a store - I rarely set foot in a supermarket - I get my produce from local producers at the farmers' market, and these producers are well known for their quality and attention to environmental concerns. In fact, many adhere to stricter standards than the USDA Oraganic code or whatever they call it. All are local. The Berkeley Farmers' Markets don't allow any non-local products to be sold - I think the radius is something like fifty or 100 miles from the city. Anyway, when I do buy produce in a store, it is from one of three stores, and I know where their produce comes from - the same local sources as the farmers' market. I do not buy ANY prepackaged produce from any mainstream producer, such as Earthbound Farms, Cascadian Farms, Trader Joe's, or other such companies. I stopped that practice quite some time ago.
You see, around here, there's a BIG movement towards buying local products, and a number of the markets will tell you exactly who grew the produce. And we have a few magazines, newsletters, and organizations that keep track of who's growing what and what their farming and production techniques are like. That goes for dairy, poultry, and meat as well.
Around here many of us are VERY attuned to where our food comes from, and who's producing it, and the quality they offer. I can tell you who packed the eggs I had for breakfast, I know the woman who raises the chickens, and the dairy products I use are only from one of two sources who produce some of the best milk and dairy in the state - and they, too, are local.
I rarely buy anything that is a commercial, national brand - well, I sometimes buy Hebrew National Franks and Grey Poupon Mustard. And three months ago - I bought a can of Campbell's soup that I saw advertised and wanted to see what it was like ...
Nope, you don't know me, and you don't know what the food scene is around here, of that I'm sure. Fortunately, there are enough Safeways and Lucky's and other such stores that, for those who will accept GMO food, mass-produced organics, milk from questionable sources, and large plastic bottles filled with chemically altered soft drinks, the option exists. And for the rest of us there's Stan Devoto and his fifty vaieties of heirloom apples, Frog Hollow for peaches and stone fruit, Lucero, Blue Heron, Full Belly amd other small, local farms growing incredibly high qualty produce (fresher and often cheaper than the stuff in many local supermarkets), there are the artisan bakers like Acme churning out organic baguettes and breads, Moyra and Thaddues Barsotti's wonderful tomatoes ... the list goes on and on.