There is lots of reasons to upgrade.
Here is a comparison:
(TL;DR at bottom for anyone that doesnt want to read all this)
Hey guys, amatuer photographer here like the most of us, this is my biggest hobby/pursuit and my best link to the art world which is something I greatly admire. I'm currently, and have been for 3 years or so which is when I got into photography using a Nikon d40 with it's 18-55mm kit lens and a Nikon VR 55-200mm lens as well as a much older Nikkor macro lens every once in awhile. I've gotten very used to this camera and I can say the 8mp has never held me back and theres a lot to love about it, I'd still recommend it to people. I'm very proud of some of the pictures I've taken on it but at the same time the better I get and the more knowledgeable I am about photography the more I notice I'm missing. I'd also like to step up from an entry level newbie camera to a prosumer camera which is what I consider myself. Reviewing the two side by side reveals a lot of on paper improvements and likens the D7200 to a Canon 70D which my friend owns and when I've used it I enjoyed immensely the experience and the pictures. I've definitely gotten over the specs make a better picture mindset but I am of the mind that newer features and better specs allow for more options than I have at the moment. My father is of the mind that none of that matters and because people were using this camera (D40) happily in the early 2000's I can use it happily today. While this is partially true, it still takes good pictures, I have the option to take better pictures. And yes the paintbrush doesnt make the painter but a better brush means a better product.
my birthday is coming up soon and Im looking to get a new camera, I'd like to ask for my parents to shoulder half (or less) of the price as my only present, I have lenses that work with the D7200 already that get the job done which makes the body only very affordable for a camera in it's class. I may even go and buy it myself a couple months later by just skimming some money off my paychecks for awhile if none of you nor I can convince my Dad of the merits of the D7200.
So the point of this lengthy post is to hear testimonials from both sides, pro and con upgrading from people who have personal experience traveling from similar cameras (D40->D7200) or more extensive knowledge in general, all opinions are welcome! Thanks all of you!