Why is Mccain running?

Last night on Hannity and Colmes they had Megan Mccain as a guest. Hannity brought up a video produced by the Obama campaign that said John Mccain admits that he can not use a computer, can't send an e-mail, and still doesn't completely understand the economy. Hannity insisted that Obama apologize but why should he? I do sympathize for Mccain since he was hurt defending our country but at the same time if you to hurt or just to illiterate to partake in activities that are essential to running anything including our country why are you trying to stress yourself and become president? It's obvious that he is to old so why is he running for president?