@bythewell - I don't think it's because the world has had time to forget. I think it's because there are all too many inequalities still around for us to remember. If the colonization of half the world by countries in Europe had just been a historical curiosity with no long term ramifications then that would be one thing.
But there are still many countries where the native folk are treated like second hand citizens. And that's why we need to have colonial discourse that takes a long view into account. If you just look at their positions today it might be tempting to say that it is their own fault, or something like that. But in reality a lot of poverty, racism and general inequality stems from the fact that one grandfather happened to have access to technology that another grandfather did not, and he used that technology to conquer.
That leaves scars and we need to see them clearly before we can even begin to try and heal them.