Because some people don't have TCCD chips with brainpower PCB, and their memory maxes out before their chips have had enough. Venices can handle 70MHz+ HTT increases fairly easily, and a lot of RAM will have trouble keeping up at that point and time. They'll take the memory bandwidth bottleneck and use memory dividers to keep increase their CPU speed.
Intel C2D E6320 / AMD Athlon X2 3800+
Gigabyte 965P DS3 / DFI nF4 Ultra-D
2GB OCZ Gold PC2-6400 / 2GB OCZ Gold PC4000
eVGA 8800GTS 320MB / eVGA 6800GS 256MB
150GB Raptor / 74GB Raptor
2x500GB / 320GB
OCZ GameXStreme 850w / OCZ StealthXStream 600w