That's a good question.
In Chin state, and as well as in most ethnic states in Burma, this is where most of the natural resources are for extraction, such as timber. There is jade in Kachin and other mining.
In the past—not under Thein Sein, the current president, but under Than Shwe and Ne Win before him—there was this policy of “Burmanization”, where they wanted the country to be one distinct nationality. They wanted ethnic minorities to enter into this fold and be “Burmanized”.
This goes back decades. This is probably the history of government policy in ethnic areas. Lately this has not been the policy, but I think some effects of that remain in older military commanders and what has happened in these areas. I think there's a lack of understanding between Burmese people and ethnic minorities, and probably racism, which also leads to this.
As far as the abuses you mentioned, the Burma army has policies of self-reliance. Most of the units are not supplied from central Burma, but they're instructed to get their supply of food and housing from the local population. So a lot of the forced labour we see is for the military—or the military stealing food from civilians to feed its own troops.
On the more violent crimes, I can't think of a reason why anyone would do them, but they might be tactics of control and bullying. We've seen a lot of that in Karen state. People are starting to say that the amount of control the Burmese army has over an area may be an indicator of how severe the human rights violations are. If they have a lot of power and control, the violations aren't as bad. If they don't have much power they tend to bully more. So depending on the regions in Chin state and what is happening, that's how we would see those different violations.