It's all the good things you get from gaming (learning from mistakes, interesting plot, social bonding from co-op experience) with none of the shit parts (fucking up and dying, grinding, etc.). If it's a particularly difficult or grueling game that I nonetheless have interest in, I can dip out til something cool happens. I get to share in their reactions and find gaming by myself a bit lonely for that reason, because I'm used to being able to share what one of us is doing. Even letsplays, I watch just as much for the commentary as the gameplay, if not a little bit more.
NotTheOnlyGamer
FrostBolt