Why can't Ukraine just surrender Donetsk and Luhansk?

Is the reason purely prestige and credibility of the government, or are there other significant economic or social issues which prevent the new Ukrainian government from thawing the crises it is still facing as of August 2014? I have read that Donetsk and Luhansk contain most of Ukraine's industry but I don't see why the government can't just support new initiatives in the west.

The reason I ask is because I cannot comprehend why a government would seek to deny a people's right to self-determination when it is obvious that such actions will most likely cause many more issues and headache in the future, as is what always happens when you oppress a large number of people.