There are a few games that I've seen this. Pokemon, Yugioh, and Chess. The reason is that it's far easier to realize that the person across from you is an actual person when the game centers on that one person. Even if it is online, the idea still exists because of this. It's harder to recognize that a team of six people are individuals.
Unless they're a Garven and you're a Lux and they won't fuckinG FARM TO GAIN XP AND END UP DYING SEVERAL TIMES DESPITE YOUR BEST ATTEMPTS TO GET THEM TO STOP FUCKING THE GAME UP
I'm also Dan,
Daaaaaaaaaan