Mainly because I'm not a big fan of automated services unless absolutely necessary (like scans and auto updates for anti-virus). I suppose it's a bit of a throwback to the bad old days of slower procs, but in my book, less services is always better, and I much prefer to take a hands-on approach when it comes to system maintenance.
In this case though, I've obviously been lax in my system admin duties......
Now currently working on a second defrag of the same partition. Did a disk cleanup after the first defrag (that took forever as well) and the compression of old files and deletion of temp files put me back into 13/33% fragmentation for that volume. The main problem is that I've installed quite a few steam games on that partition, and probably haven't thought to do a defrag in at least 6 months so it's a mess....
edit: I'm also not used to having so many "small" game files to deal with on a single volume. Before I started using steam, any game which hadn't been played in a month was removed from the drive until I decided to play it again. With the majority of my current games being dl'd from steam, I'm reluctant to uninstall them as I haven't backed them up and thus don't want to have to dl them again......