What it really is though is unpolitic. Especially in the USA, suggesting that something can wait, or that the morale boost from working less will end up in more productivity angers a lot of people.
"They're out of their minds! They suggest that it can wait and the morale boost from working less will end up in more productivity... Blasphemy! They're just lazy! I've worked 90 hours a week for 7 years, and because of that I'm ill and borderline insane, but IT'S WORTH IT, I'M PRODUCTIVE!!! Sure, I'm chronically stressed and made 3 burn-outs, but I get stuff DONE. Those no-goods can't understand what it's like. They don't understand what sacrifice means! Grumble."
That being said, this doesn't mean Americans aren't the most productive overall, since Americans do work insanely long hours compared to Europeans.
I wish I could find the study I read last year that found only about 20% of hours spent at work by a typical worker are productive, but I'll have to settle for this: http://www.nytimes.com/2007/05/31/fashion/31work.html
Working fewer hours does not mean you do less work. Indeed, the improvement in efficiency can mean you ultimately produce more. It's like if you drive a car at 100mph everywhere, you'll use more gas per mile than driving at 55mph (indeed, this was why that limit was set).
(Update: Heh, just noticed someone else used an automotive metaphor above!)
Urgency = putting out fires
Importance = creating value