The issue is summed up in another paragraph in the article:

While many hybrids attract customers based on fuel economy, Honda tuned the Accord hybrid for power, leaving it with mileage similar to the four-cylinder version but a price tag that can be $5,000 more than a V6 model.

The hybrid Accord (V-6) is rated at 25/34 mpg. The non-hybrid V-6 is rated at 21/30, and the non-hybrid 4-cyl is rated 26/34 (manual transmissions).

What this is showing is that people are attracted to hybrids by sizable leaps in gas mileage. They want to see mpg ratings in the 40's and 50's, like the Prius and Civic. That's what hooked me into the Prius, and it was only after getting one that I discovered it's a pretty darn nice car as well.

The hybrid Accord isn't selling well because it isn't giving people what they want. In the long run, perhaps demand will pick up for higher powered hybrids, but it doesn't seem to be there initially. Why pay the extra price and take a risk on new technology when there isn't much to be gained?