Why do Serbs want Kosovo to remain within their nation?

First Kosovo is 90% Albanian. Serbs have treated the Albanians very unfairly over the years and especially prior to NATO intervention. The region was the poorest in comparison to other Yugoslav republics. Yes it once part of Greater Serbia but so was Skopje and other regions currently in different countries. The Albanians want independence, so why will they(Serbs) not honor the wishes of the people residing their? I want logical and reasonable answers all B.S. to the side. Do not come her and write "Kosovo e srce na Srbija" or other childish post. Valid agruments. I'll discredit the claim that Kosovo is heart of Serbia here and now. Can any Serbs answer this than? Why have scores of Serbs left if it was the heart of Serbia over the years? I'm not talking post 1999. Mature posts please!