From her very first match, Serena looked like she didn't really want to be in Beijing. She looked like she was forced to be there. She said she was tired after the US Open win and even withdrew from Tokyo citing fatigue and exhaustion. Fair enough. She shouldn't have to play if she's tired.
I'm just speculating here, but maybe Serena was reluctant to play in Beijing and wanted to withdraw from there as well, but was coerced into playing, either by the WTA or by Patrick. She wouldn't care if she was fined for not playing. She skipped the entire Asian swing last year because of injury. Maybe she just wanted to rest after New York?
But anyway, it could still be for any other reason.
Even me was so bored to cheer for her this week. Seriously, she needs to take a break to get more pumped up.