AnandTech had an interview witht he founder of PC Power & Cooling:
Why are the high-end power supply manufacturers still pushing such high wattages?
DD: Systems with multiple CPUs and GPUs can actually draw around 1000W. In other cases, users want the advantages associated with operating at 40-70% capacity. These include wider input operating range, longer hold time, lower noise and ripple, cooler, quieter operation, and longer product life.
And this is good for the companies of course because they make higher margins from higher wattage models?
DD: That's not necessarily true. The margin on the Turbo Cool 1200 is below average because the unit uses expensive low-volume components. The real advantage of building high wattage power supplies, besides bragging rights, is that it moves our proprietary technology forward and that knowledge can then be used to improve the performance of the high volume midrange products.