Actually they could fit two in SLI, but all Apple wants is our money, so they didn't.
Then they would have to include a USB-C to external fan adapter or make you buy it for an additional $80. Lol.
But really, for simple or older games it should be alright. But it may throttle the heck out of it. I'd say it's possible if developers wanted to. Even my old iPod touch had some decent looking games with a fraction of the power.
I have fond memories of playing games on my Late 2008 MacBook with the GeForce 9400m. It played TF2, Portal 2, Call of Duty 4, Burnout Paradise and more perfectly fine. But those are older games. The last thing I tried running on it before I sold it to my brother was probably Dishonored. It wanted to run but wasn't really playable. Crisis on the other hand ran on low

Some guy on YouTube ran Crisis 3 on the MacBook Air a couple years back too.
So it could be done I'm sure. But throttling would be it's downfall. Just get a console or something. Or grab the MBP. For example, my truck is fast when it needs to be, in a straight line. But it isn't a sports car and I can't expect it to handle like a BRZ when it's 6,000 pounds (though it's faster 0-60 than a BRZ

). It does what it is designed to do though, and it'll pull our 9,800 lb tractor and plow through snow like nobody's business.
Edit: This would be perfect for it!