Why is the Vatican, that centerpoint of the teachings of Christ, be in Rome? The reasons are historic - Jesus, of course, never visited Rome. But in those far off days, Rome was the center of political power.
Why is the Vatican still in Rome? Most catholics don't live in Europe, never mind Italy or Rome. The greatest growth in new Catholics are in the 3rd world, the greatest declines are in Europe. If Catholicism were a business, it would long ago have relocated its decision making center to follow the growth.
Are there any religious reasons why the new pope shouldn't simply move the Vatican to San Paulo?