Over Clocking is a hobbyist pastime.
The people who buy workstation level computers are more interested in the fastest speed that can reliably do their work, not speed for speed's sake. That is why most workstation level machines opt for Fully buffered Error Correcting Circuitry RAM rather than cheaper, faster RAM. It is a trade off of accuracy for speed.
I'll take the 24/7 Prime Torture Test stable Overclocked machine.