re: "it's in the Kurds self interest to be part of Iraq"
"Th only reason the Kurds play ball is that if they did not, they would be surrounded by hostile countries, each of whom has a grudge against the Kurds. A landlocked and distinctive group has serious problems if they won't knuckle-down to their neighbours' expectations..."
There are these hard power considerations but obviously also the soft power considerations. You should notice in the link Marcia provided that the Kurds referred to Turkey's inclusion as a matter of Iraqi concern rather than just a Kurd problem.