It's for the cases when you are in a different timezone than the server. When the log says "03/Mar/2013 09:24:13 -0800" and it's 13:50 where I am, it takes me a while to understand how old that line is.
I know it's different, meaning that I have to do some basic arithmetics to get the log line age. It also requires me to roll my precious eyes to look at the local time in a system tray. It's just all too tedious.