You punish people to deter others for committing the same crime. The other benefit, revenge, has a scope that is too narrow to benefit the masses. So, if you are replacing an evil regime with a new regime and there is no possibility that the old regime will come back (apartheid has run by a small minority of the population) then there is no benefit from punishing past crimes. This is why the "truth and reconciliation commission" was so successful.
Very few countries can boast to such a peaceful political turnaround.
I'd say most countries in Eastern Europe and some in South America certainly can boast that. Political changes don't nessecarily have to be bloody, violent affairs.
Or such a slow descent into tyranny. Let's see when Julius Malema and his supporters eventually do call for the eradication of white people.
Conversely the South African "truth and reconciliation commission" seems to have played a part in the healing of that country - but at the cost of leaving crimes unpunished. Northern Ireland has opted for an intermediate approach of trying to draw a line under everything as quietly as possible - no truth, no justice, but no more killing.
Arguably many of the US's current problems stem from inadequately addressing the pro-slavery faction. At least now the question of "what is the significance of all these statues from the losing side of the civil war?" is back in the public consciousness.