Hobbies And Interests
History
No console before the PS2 had such connectivity, instead acting as insular, standalone devices. But despite Sega's Dreamcast delivering a modem out of the box, something the first PS2s didn't, having USB included allowed for greater expandability upon launch in 2000--the U.S got its PS2 in October of that year. All revisions of the PS2 have USB ports, and all are backwards compatible. Let's look at what these make possible.
Keyboards and Mice
One of the most exciting aspects of having USB connectivity seemed to be the ability to use the same keyboard and mouse known from PC usage. This is indeed the case, but the problem is, the PS2 is still primarily a games console, and very few games released for it ever bothered with keyboard and mouse support. So while the console hardware does recognize these two peripheral types, the software has very little use for them. Games that do enable keyboard and mouse seem to be more sluggish than when played with the regular controller.
EyeToy Camera
EyeToy is a technology developed for the PS2 that uses a camera to capture gamer movements and appearance for use within certain games. It's essentially a scanner, and the connection method is USB. This is probably the most successful and widespread use for USB devices on the PS2, having been responsible for the release of several titles that support this technology.
Headsets
Shooters such as the SOCOM series debuted the concept of in-game voice, necessitating use of a headset and microphone. On the PS2, many of these are USB-based, affording easy connectivity and detection. Their popularity isn't that great, mainly because online gaming didn't catch on in a big way with the PS2.
Removable Storage
USB sticks and flash drives have been available for the PS2 for some time, acting as removable storage. When connected to the console, and if properly USB certified, the removable storage device can accept files from the PS2 and vice versa. Because of their low cost, these USB devices are a more cost-effective solution than Sony's own memory cards.
Controllers
Beyond the stock Dual Shock controllers, USB connectivity has provided the PS2 acceptance of a wider range of devices--these include old-fashioned joysticks, arcade-style controllers, racing wheels and flight sticks. Unlike some of the other peripherals mentioned in this article, these have had wide support among game developers, and work well most of the time.
Considerations
After over a decade in the market, the Playstation 2 has made some use of USB, although its inclusion didn't really have a dramatic impact on most users--who remain first and foremost gamers, and therefore comfortable with non-USB devices.
Support has also been an issue. First, even if the console does recognize the USB device, actual utility depends on the software--and thus is beyond Sony's control. The company also makes a big deal of USB certification, which in other words means external USB devices must be tailored to the PS2 in order to work.
In short, unlike its more evolved relative the PS3, the PS2 has little use for USB and it should not be a determining factor when using this console.