Do you feed your kids junk food for treats?

Neither me or my fiancee can bring our selves to give our two kids things like a biscuit or a piece of chocolate as a treat, albeit one is six months old so he doesn't eat solids yet as he's still fed. All of my step daughter (That's what she'll technically be when I marry her mum but I prefer to call her my daughter) friends and family think it's silly she's never eaten chocolate or a burger or drank fizzy pop. We lead pretty much an organic, additive free life. We grow our own vegetables, support local bakeries, farmers and butchers. Are we wrong to not let our kids eat junk food? The kids are slender and not fat like many kids are becoming from eating junk food.