What's the deal with half wrapping bars?

It's what they do at the track to reduce weight. No need to have tape on the tops. It's replicated on the street because it looks awesome. Personally I prefer the keirin grips which are mega-awesome.

Yeah, that guy's saved even more weight by only having a left-hand handlebar. Also more streamlined (the second arm goes tucked behind the back, like a speed skater).