>>1484288+1 for being crazy, stupid fun.
Basically, you have a lightweight, agile bike, with no unnecessary gear (pun intended). The lack of a groupset (and sometimes brakes) means that even with a heavy brooks saddle (510 grams, yo), and a steel frame, you have a bike that weighs ~9kg, and lets be honest - having a 2x10, or 2x11 groupset is kinda useless in the city, as you mostly use 1 or 2 gears anyway, and the direct power transfer of the fixed gear is nice, and responsive.
If you have a chance to ride a lightweight fixed gear, try it - it's great.
Pic related.