Why people like to see pornographic scenes, but do not feel the same about eating scenes?
Well, the whole point of watching porn is sexual arousal. (Or research for the curious, but that's another thing)
Watching someone eat delicious-looking food CAN make people feel hungry. I admit, I have a bad tendency of feeling hungry if I see good food, or if I see someone eating good food.
But I don't get the point of the question. Are you wondering if most people feel this way about watching someone eat, or are you wondering if people are AROUSED by watching someone eat? Lol. Some clarification would be useful.
EDIT: Ok, I think I get it now. You're wondering why aren't there any "food scenes" for food-loving people? Well, it's not as widely prevalent as porn, but it IS there for those who are into it.
^ One of my favourite sites, actually.