To play both factions. I normally build clones of each class I play. One on each faction. Some* days I'll switch to the losing faction to try and balance out games. Other* days I'll log to the winning side because losing just isn't "fun" when it gets to double digits for games lost. Also, I'll log to the other side if I see some friends online that I would enjoy healing. Lastly*, I'll log to the other side just to spite someone who macro spams me in a negative way.
*Rare occasion
*Rare occasion