why is that illegal to run bitcoin exchange? its not real money
It's being exchanged for real money. Therefore, according to the law in Illinois, you have to have a Money Service Business license or face felony charges. I am not a lawyer, but...
... the money transmission laws and regulations are written very broadly. They almost certainly apply even if you are exchanging one crypto-currency for another, and no "real money" is involved.
The only saving grace is that the laws only apply if you are operating "a business" -- so occasional lowish-value person-to-person exchanges done as a favor to friends at no markup from the current exchange rate is probably perfectly legal.