It was explained to me at a Microsoft recuriting session that I attended a couple years ago that if you work for engineering at Microsoft your job title is either Designer, Programmer, or Tester. People who do one don't do either of the other two. (Although, surely there must be some niches like their research department where cirumstances are otherwise). So, since all Programmers are confined to the straight-jacket given to them by the Designers, the ability to optimize is probably the best way to differentiate the good ones from the mediocre ones.

Needless to say, I wasn't impressed by the recruiter's pitch. Then again, the recruiter probably wasn't impressed by the Tux polo shirt and EFF cap that I arrived wearing :-)