I build because I do not end up with all the crapware that comes installed on factory PCs, I can build to meet my needs, and I can install the OS I want.
EDIT: As for the PC you linked, not bad. I always had good luck with HPs back when I was buying them and that has plenty of storage and memory.
www.pcdecrapifier.com is the first thing I run on every new computer. Followed by www.ninite.com