The reason to make changes now would be so that they're set in stone before the next administration comes into power and tries to change everything back. This logic applies to every agency, and is one of the reasons NASA's Ares system got cancelled so quickly by the Obama administration (before they had an alternative vision for space exploration).
The reason to privatize this one is because it has direct competitors, and does not accomplish anything which requires the powers of the federal government. Other departments such as the Department of Energy are not interchangeable with a private competitor, and perform functions which require direct federal involvement (guarding nuclear weapons and working with the armed services).
Some people (including myself) believe the federal government should be as small as possible, and the USPS is simply one of the easiest parts to spin-off/get rid of.
The reason to privatize this one is because it has direct competitors, and does not accomplish anything which requires the powers of the federal government. Other departments such as the Department of Energy are not interchangeable with a private competitor, and perform functions which require direct federal involvement (guarding nuclear weapons and working with the armed services).
Some people (including myself) believe the federal government should be as small as possible, and the USPS is simply one of the easiest parts to spin-off/get rid of.