This has always been an annoyance to me, and always justified with "good design principles."
What is with this ?
"Your web site is boring - what's this, 'black' text on a 'white' background? Let me redesign your site, because I am God's Gift to Web Design and Know Everything. We will kill your conversions and visits, but man, it will look COOL!"
Is is that cool ?
Heck no. It's trendy, hip, Web 2.0, but not cool. :-(
Who started this trend ?
Why do people do it ?
Don't know, don't care, "forgive them, for they know not what they do" (and don't care, see trendy, hip . . . )
Surely you want people to be able to to read your content ?
I love the responses to this one. Almost all of them are the same with variations. "Our target market is X age old and actually prefer light gray type on a low contrast background. We've asked everyone we care to listen to - they all love it. Basically, we don't give a c**p about anyone else, so their opinions don't matter." And the really SICK thing about this? Since their visitors are a "skewed set", this spills over into self-gratifying statistics presented at board meetings and assessments, so the site owners never even know it's happening.
When will a trend back towards black start ?
Set your browser style sheets to a **legible** contrast and override theirs. They really don't care.