Like Doc Bolens says, there are degrees of restoration.
There are the full blown, down to the nuts and bolts, all factory correct restorations. Many actually looking better paint wise than what the factory produced. Usually these are the ones that end up as show only.
Then, there are what I prefer to call REFURBISHENTS, where the tractor gets put into good mechanical shape and a good/decent paint job. These tend to be working tractors.
My 1886 forklift is a good example of a refurbishment. It was not a total teardown, it's been repainted in a non factory color scheme, and has other parts that are non-factory. This is being done to preserve the history of the tractor as much as possible, rather than take it back to factory correct. It will also be a worker rather than a show piece.
The rest of my tractors are all 'original condition' ones and are workers as well. I personally think that they deserve to be used in the manner that they were intended to be used. However, I can't fault the folks for not using a tractor after doing all the work that it takes to produce a show piece.