Because white ,ology graduates who read the Guardian seem to wish it , makes them feel better about our shameful history.
Self flagellation over past events doesn't really help. Perhaps you should consider instead some of the advantages we gave to these people with our inventions, medical knowledge, schools, and the fact that after independence we left them with democracies based on our own and copied by the rest of the civilised world.
Where would these people be today if we hadn't had our empire? I'll tell you, running through the jungle with spears trying to catch their supper, dying from curable diseases and fighting wars with each other just as they were 300 years ago and many are still doing today. They hadn't advanced in the thousands of previous years, why would they have progressed in the othr 300?
Personally I'm proud of our great history. The world could not function today without the things we invented and dicovered in all fields of science,medicine, engineering, agriculture. And the world would have none of them if we hadn't had an empire to recompense us for the cost of giving them to the millions of people we then ruled.