Well, first of all, it is masterfully done and a beautiful plane. I would like to know how you fit the engine covers so that they are removable, yet held in place so perfectly. I was afraid that all of that beautiful engine work was never going to be seen again.
As for the motivation, I think one needs to have a goal, or some reason to be excited to build any model. I have only built one other Spitfire, so building this one is still exciting to me. I was almost school kid giddy just opening the box. The scale is also something I have never done, and the level of detail is scratching many of my art minded itches.
I agree about cars and tanks. The level of detail still visible after assembly is very gratifying. Working to create a flawless car finish is a joy in itself. Being able to open hoods and hatches to see the work beneath can be very satisfying. It is why I am so interested in how you can remove the engine cover. What holds them in place when covered?!
So, I guess, in conclusion, the reason behind why one opts to build a particular model has a lot to do with the joy or lack there of. To build it just to build it may not provide that? Personally, I am extremely glad you decided to build this particular model, as it gave me lofty goals for building mine. The Spitfire still fills me with pride and awe for the British people. To me, it is a symbol of tenacity, bravery, and engenuity. I want to thank you for building this plane as a people, and this particular model as an individual.