He's too lazy to run for President. The Obama's are living like the King of Siam since leaving the WH. They know they never have to 'work' (as if they ever did) a day in their life. So why bother?
Maybe, like Bubba and his wife, Obama dreams of being a shadow President. Maybe. But I'm pretty sure he is happy slacking and getting stoned every day. So again, why bother?