Why so FEW cities? He has 40 concerts! You are kidding, aren't you? I can't imagine this schedule, and with only two months to get a tour in, I'm super impressed that he has the stamina.
I think that major cities were choosen as it is easier for transportation in and out. I don't live near a major city, but it is EASIER for me to get there, than for many people to come nearer to me. Seems pretty logical, don't you think?