This makes it convenient to link in support forums or (even better) in your signature (see my sig below) and standardizes presentation for comparative purposes. These specs can also be linked to from any other 'presence' our users maintain in other parts of the web.
... so if you post on Reddit (or a blog or whatever), you can add a convenient link to your system specs, courtesy of STEP
Adding your system specs also sets us up to relate user configurations to performance once we have that configured
PS: also notice the link to create a mod page on our site, which is a welcome contribution that helps us out! (just be certain that the mod page does not already exist under a similar name! ... else we will have a redundant mod page)