There might be different reasons....
The lack of interest by the public for U2 music, political/security reasons, they never played in a muslim Country.....
Personally I think the first one is the main reason
Aww.. with U2, it's not like they don't like travelling of visiting new places ( how many bands stop off in Tel Aviv?)
With most huge tours like U2 run, the big issues are usually cost and logistics. It costs a lot to go to 'new' or far off places in plane fares or buses & trucks, and to haul that much gear around and find places to stay for that many crew people, it can be a big headache! Then you need a big venue with great sound equipment, enough power, a local company to sell the tickets, etc
Some places are harder than others to run a big rock show. Much sympathy to you in Turkey! ~Ultra
Turkey is a 98% muslim country... "Coexist" while SBS... "Jesus, Jew, Mohammed it's true - All sons of Abraham"... i don't think they would get it in any other way than taking it for western blame of their religion, just as they did it with the cartoons, the pope speech, rushdie...