The failed ones are recent which means the outcome has the potential to change in time.
Would an 80% success rate over the last hundred years change your perspective?
People who live in those places rightfully do not give a flying fuck about westerner's perspective. They care about being killed, maimed, displaced, robbed of the source of income etc. etc.
I can only imagine what would happen if you stood in front of them and tried to explain your stats.
Additionally I am not convinced that a independent Kurdistan would be a good idea.
I know Abdullah Öcalan has come under the influence of Murray Bookchin, and has had some very progressive ideas about how the politics of the Middle East should be structured. But in the event of the establishment of Kurdistan there is no good reason to believe it would be any less of a dictatorship than Iran, Turkey, or Dog help us, Syria.