It's the simplest BG, the most balanced - and a few good players doing objectives and peeling can win the match regardless of whatever else is going on in mid. It's a smaller bg (10v10) which means your individual power over the outcome is higher (1 of 20 participants), rather than AV/IoC where 80 people are doing things for or against you.
When you lose, you know where your team went wrong and what should have happened instead. It's more about how easy it is to take the losses in WSG, rather than something like AV/IoC where losing makes you feel powerless. Negative feelings stick with us far more than the positive feeling of victory.