Must be a good reason - probably "security updates"... Geez, can't they just release one firmware version every few months instead of every week? Or test their hardware + software more thoroughly before shipping...
From Sony's site:
An update to the PSP system software was made available on September
13, 2007. With this update, the system software is version 3.71.
Features updated in system software update 3.71 include
Security
- A correction has been made to the settings for some regions.
Note:
- This system software update includes all features contained in previous versions.
- The new system software will preserve any settings previously made to the PSP (such as the Parental Control level).
- Depending on the software title, you may not be able to play without first updating the PSP system software.
- Do
not perform updates using any data other than the official update data
provided by Sony Computer Entertainment over a network or on disc
media, and do not perform updates by methods other than those described
in the product documentation or in this site. If an update is performed
using data from another source, by another method, or with a PSP system
that has been altered or modified in any way, the PSP system may not
operate properly and may not be able to install the official update
data. Any of these actions may void the PSP system warranty and affect
your ability to obtain warranty services and repair services from Sony
Computer Entertainment.
Source:
Sony