I think it may be as standard as using DOF to seperate your subject from the background in those types of shoots, but the actual style of shoot itself isn't exactly the bread and butter of portraiture. People had until recently (or so it seems with the current upsurge of examples) been doing their shoots of people or whatever using a more balanced exposure.
FWIW, I like ring flash shots and the mismatched ambient/flash shoots, I just hang my head in despair and think about CDS' dog's nuts when I see how many people are jumping on the fashionable bandwagon. Fine I guess for fashion shoots where the very essence is to produce the latest and greatest fad, but on cars say, I see a lot of publications using it all the time, and I can name several car mags where the general photographic content has gone from pretty bloody good to 'look what we're doing this week' fashionable...