I do it whenever I can. I'm a left-footer, and can't stand for a dime on my right... but one day, while I was trackstanding at a light for about 45 seconds (maybe a minute?) a guy walked by and said 'wow, I wish I could hold it for that long'

THAT makes trackstanding worth it! Really though, it's a fun challenge to see if you can not put a foot down the entire ride. Necessary? no, fun? yes.

also, I was riding home a mountain bike I bought the other day and was able to trackstand all the way through a light. It was a really neat feeling to do that on a freewheeling bike, I felt so accomplished!