Food ads aren't exactly making health claims ("this ice cream is delicious!")... and to be honest, I'd think a better question is why you ever thought that corporations trying to sell their products would particularly care about your health.
Also, the new wave of "you can have X as part of a healthy diet" is essentially a response to consumers wising up - whilst technically the same is true for shaving cream, it's now your fault for getting fat because you don't run three marathons each day to burn the calories from that delicious sugar coated with a little bit if cornflakes