Why dont people cook for the their dogs?

Well I just recently got a puppy. I was doing all kinds of research about what to feed my little baby. Except there was so many different sites, and too many different answers. Some say its good to actually cook them real food. But others state it isn't the best idea for someone to do. I mean I would love to cook her real food if I knew for a fact that it is he deed a good thing for her. And I remember reading about the call back on all those bad dog foods that they had, and I am currently trying to figure out what to do. I mean I've taken her to the Vet and he even saw her before we purchased her, and she is doing fine, except the fact she as a sneezing problem and I'm not sure why, he told us to give her children's benedryl (spell check on that one...sorry) and well she hasn't gotten any better so we stopped giving her that and we have to take her this weekend to see the Vet again, cause it makes me sad to her sneezing all the time. Do you think it's possible because what we are feeding her, that she is sneezing so much, or am I just going crazy??