Why the originals?
My answer is based on my personal opinion and beliefs. I find a special quality in most of these original instruments that I can not find even in the best copies. The copies are sometimes even made somehow better than some originals! but maybe it is because of the soundboard which is the heart of the instrument that differ from the originals...
In those times, they used the best wood for the soundboard, please refer to several articles about this, like Martin Skowronek's book or the German book '' Das Wiener Klavier bis 1850''. There you will find out that what we get can not be compared to the quality of the old soundboards.
We run out of many things in this 200 history behind us! another example is the real mahogany which is nowhere to get anymore!
Back to the personal feeling I have about the original instruments which is beyond the physical declarations of the wood and material, it is about the other side of a historical evidence. The piano we can imagine as an example is the Carl Holsoe piano. It must have been made in 1770 or so, someone bought it, played on it at home and maybe accompanied songs etc.
lived in a totally different time and experienced different occasions. It lived for many years in different enviroments...one of the was for a few decades with the famous Danish painter Carl Holsoe...he has expressed his feelings and art in several paintings where this very piano is located and is even in the center of the painting. People were born and died, wars, celebrities and other things happened and this piano still lives and luckily now with us in this collection.
It is 240 years old and is still living...a new born piano no matter how clever and well made, is new and will also live hopefully for very many years and no one should/can see it with less value but the old piano or the old violin is another creture with all things that has happened to it, it feels the inviroment and reflects stories and though our feelings may not be that powerful to be able to hear its living voice, one may find a special sense to it. Wood, painting and such things do live with us and save the historiy in themselves. Maybe one day one can see and listen to their story by some techniques that we have not achieved yet.
Scientists are working on recovering the sounds of the past...sounds that were produced in the atmosphere and may be recoverable from what we think as nullity, absurdity...because they believe nothing disappears entirely. Like material that does not disappear and transforms and remains in the nature.
So I believe the history that the instrument has had experienced is saved in its essense and will not go to nullity.
All the body of the instrument feel the music that has been played over many years on them...I believe even the manner of its owners and performers and atmospher of the household will remain in it. An abondend instrument which has almost never been played and has suffered damp and dust over many decades will also reveal its own sad history!
This might sound none logical and not scientific enough for those who only believe in their eyes, but this is my own impression about my Viennese violin ca.1770 and 55 fortepianos of ca.1760-1840! and many other original instruments known to me.
I wanted to share my thoughts and feelings with you. These thoughts may sound oriental in the wester culture but I myself come from the orient and have a strong feeling about the early music and early instruments and generally the spirit of sounds which require spiritualy talented ears and hearts.