Hmm... I'm no Gourmand so I couldn't tell you all the reasons, but I can tell you some things are better eaten together and are also more filling that way. Like, I could wake up and only have toast in the morning, but that's pretty dry and doesn't have much flavor. But if you put jam on it, it tastes way better! That's a simple example, but you've probably had a favorite meal or food before, right?