I really don;t think that's always the case. None of my large cents have ever been cleaned by me and they sure didn't appear to be cleaned when I got them 50 years ago in cardboard flips. I think this might be the case in a lot of private collections ? gary
In the early years of " Coin Collecting " giving a coin a " light cleaning " was acceptable and even encouraged by the Numismatic Community . I'll even go as far as to say that many of the TPG encapsulated coins from the 1800's and early 1900's have been given some sort of " Light Cleaning " .
I think you both are correct. At the same time there are still lots of raw copper that could be graded. Of course - market acceptable cleaning is the key. I also seem to recall one of the larger famous collections had some that were worked on. I recall this because I found the original sale on heritage and the coin was now raw(and my opinion) looked nicer. Somehow the stains were less noticable. I thought the coin would re-grade. I think when buying raw you need to make the coin and price line up - in this case you could get a nicer original coin for same price(as mentioned).