it's actually easier to navigate in traffic because of the geometry. indie/hipster kids are always looking for new trends, and fixed-gears are associated with the DIY culture that's getting popular right now. i'm on a track team so i actually ride at a velodrome and for me it's a lot more fun than regular road races.
the appeal of fixed-gears (other than being a fashion statement) is that they're simpler (no derailleurs, no shifters, no cassette, usually only a front brake if any), more mechanically efficient, they're lighter, and for some, fixed-gear freestyle riding (similar to bmx) is getting popular.
been riding fixed for 4 years, track cycling team for 2 years, worked as a messenger, ride in criteriums (road races), biked across the US last summer, worked in a bike shop, built a few fixies