The reason or reasons I can think of are fresh, never moved coins. With "fresh" coins you are the original owner, there is no chance that those coins were used in anything that could be seen as risky and no one had possession of the coins prior to you, the coins were generated then sent directly to the collectors physical bitcoin. There are probably other reasons as well.
It makes perfect sense that. I would like to buy bitcoin miners always, without past, clean coins. I would also sell bitcoins always good person.
No one knocking on my door asking why I negotiated with suspicious people.
Bitcoin is not anonymous and would not want to be in the middle of the hunt trail for a villain.
This vile world, a bitcoin transaction carries on his shoulders more than a bitocin value, but also the reputation of your origin and destination.
If it were not so, there would not exist bitcoin mixing services with the frank intention washing.
paranoid, but good idea.