Image files are like cookies.
An image, saved as a .jpg, is Nikon's fully baked cookie handed to you on a platter. It's baked and ready to eat and composed of those ingredients that Nikon thinks a cookie should have based on the information presented to it at the time. These cookies are, generally speaking, pretty darn tasty too. Sometimes the flavor is a bit off, sometimes it can be way off, but that's too bad because Nikon baked the cookie and handed you the finished product. If it's missing all the chocolate chips YOU think should be there, tough noogies. You also have no idea, really, what went into the cookie because all that information was thrown away, so making changes to any particular cookie, while not impossible, is awkward and limited. Still, most of time, you get a pretty acceptable product when you go this route.
An image, saved as a RAW file, is the dough for making Nikon cookies. All the information about how to make it into a proper cookie is there and all the information you could want about the ingredients themselves has been preserved for you. Further, you also have all the basic ingredients that went into making this dough so if you want to modify the dough before baking you can. In short, with a RAW file you have everything you need and all the information possible to modify your cookies as much or as little as you want. Yes, it's more work to go this route but you wind up getting the EXACT cookie you want EVERY time. Your dough can be pretty whack and even that's okay because you have SOOO much more workable latitude because even the information about the ingredients that went into your cookie dough has been preserved and can be tinkered with. Taking this route you can get the exact cookie you want every single time. It's also why your .jpg files look better, generally, out of the box than your RAW files, do. It's a question of who is in control of your cookies.
Your RAW files are just that, raw... They're waiting for you to come along and tweak them to perfection because you've decided you're tired of simply taking what Nikon thinks is best. You want to be known, not as the guy with a great camera, but rather as the guy that consistently "Nails the Shot" and gets the oooo's and ahhh's. You're tired of hearing "Oh, nice picture"; you want to hear "Wow!" In short, you don't want to "take pictures" any more; you want to "create photographs".
