Our ignorance of the cultures (positive and negative) in parts of the world where colonization did not happen is motivated by something less pernicious - people are parochial, and European culture in particular took a fairly strong stance that despite knowledge of the civilizations along (e.g.) the silk road, they were of no particular significance since they didn't have (Jesus|Bach|Newton|Galileo|etc.)
You ask "to what end?" I would say the end has multiple components. One is that history rhymes and so if you want to understand the future better, understanding the past better will often help with that. Another is that cultures themselves carry the past forward for amazingly long periods - the English have still not really abandoned the Norman conquest of 1066 as a socio-structural signifier even though it was nearly 1000 years ago. The Hopi still have many stories of things that occured in their world 600-1200 years. If these historical stories are inaccurate, a culture is doing itself no favors carrying them forward. And similarly, a culture that carries such a story as a tale about injustice is not done any favors by being told "ah, fuhgedaboutit".