Actually it is possible, and it's not hard to juggle two games once you train your eyes. Like I've mentioned before, there's a lot of stops during a game - free throws, timeouts, dead balls, fouls, etc etc, that you can just focus on one game at times. And I mean it's not like I don't ever pause a game while watching another and come back to it later. I'm not constantly watching two games at once, and I don't usually watch the closing minutes of games if there's a blowout and the second units are in.
Do I miss the odd play by trying to watch multiple games? Sure. But same goes for everybody when they're not paying attention, looking at their phones, talking to someone, doing another activity etc etc.