This is wrong though, if a coin is seized then it means the person that received the coin the first place did it illegally but I want believe that the coin has an origin, why not send back the coin to the original owner. I can't imagine someone coin was hack and lose everything they have fault for only for another country to hold into it. The only coins that government is supposed to keep is only when someone use it for terrorism or use to trade illegal goods.
I remember how silk road Bitcoin was sieze years back, he even went for prison for it because it was reported that the Bitcoin in his possession were gotten under the influence of dark web and any activities on dark web is illegal, he was later pardon but all the Bitcoin was taking by the government which was understandable, he got back though because people still donate some Bitcoin for him after his release, that's one power message of a decentralized community.
Your own example contradicts you. In cases like dark web markets, the users are using the coin for illegal purposes and the sellers are getting coin for illegal things. In both these cases there is reason to return the coin to anyone, so it should be seized and go towards the government. For other cases like scams I have explained it in my post.
In that case the seized asset should be given back to the victims.
In many cases this is near impossible or does not make economic sense. Should they spend $100m in taxes to track down, account and reimburse victims $10m in value? No.