Because it's their value line. Gee, it has the Asus northbridge HS on it, will that change your mind
The K8S8X is a value board meant for cost conscious consumers; thus it gets sold under the Asrock brand. I'm ecstatic, leave off the Firewire, Gigabit LAN, and other junk and keep the price low - my local distributer quoted $90. The huge bonus is that (1) it's the best performing A64 mobo out there, (2) it's made by Asus under a subdivision so it's quality, and (3) all the functionality (like LAN and SATA) is on the Southbridge so performance is fantastic as the only thing fighting for the PCI bus's limited bandwidth is the sound (whether the integrated or an add in card).