That is not the point. There are a lot of things in the world that may remind someone of something bad. Take a look at history books. Should we not keep them either because they remind people of bad things? Of course we could use a zillion other things besides "history books" or ".su", the point is the reason behind not keeping or removing them.
"History books" have value in aggregating and presenting information with historical context. TLDs are artifacts without context. A history book that covered the 20th century and blandly mentioned that the Soviet Union was a collection of communist states, without mentioning any other events or context, would be similarly irrelevant, and should be relegated to the trash heap. Same with the .su TLD. We should definitely keep the historical records that it existed, but there is no reason to continue its actual existence at this point.
Those domains have value, too, to the owners, for one, and perhaps to its visitors.
> there is no reason to continue its actual existence at this point.
I might as well just reply: there is no reason to not continue. Why should we take away people's domains just because you think there is no reason to continue its actual existence? Put yourself in other people's shoes, please. Imagine if someone used this reasoning to get rid of or take away whatever you are fond of.
Perhaps these domains have no value to you, which is fine, but we should not get rid of anything just because they have no value to you.
