Because the people are terrorised by the Mugabe regime and have no organisation or means of revolt. If you ask me, the UK should have gone in and removed Mugabe by now. I do not believe it would be hard to convince the British public that it would be the right thing to do, what with Zimbabwe being a member of the Commonwealth, and Mugabes attrocities plasterd on our TV screens. Mugabe is the man who recently called himself "the Hitler of our times". I do not believe the Zimbabwe military would give much resistance, as personally I believe their support for Mugabe tyo come from a few key players, while the majority just follow blindly. I believe it would only take a Para batallion or two, supported by some light armour and a Logistics batallion, to rapidly destroy Mugabes regime. With Mugabe gone, we could immediately turn the power of government over to the opposition government, with an election date set for a couple of years away, while keeping a small peace keeping force to ensure the oppositions survival until that date. I reckon we could be in and out within two years tops.

My guess is that many of the Rhodesians with military experience left Zimbabwe in the early 80s for South Africa. So, they don't really have vested interests in Zimbabwe at this point. It could happen though.