In virtually every Video Game Party I've done so far, a young guest asks if they can play a game in single-player (or story) mode. And almost always, I have to say no. I have an easy "go-to" excuse: that playing in story mode monopolizes a whole TV and game system for that one guest; multiplayer mode allows other kids to play instead of wait. But sometimes it's a small party, so that excuse doesn't work...but I still have to decline most of the time.
The reason is, especially if the game in question is rated M for "Mature" by the ESRB, is this: in story mode, there's likely to be more adult content. In Call of Duty: Black Ops III, there's all kinds of F-bombs and other strong language. In the latest Grand Theft Auto installment (GTA V, which is not part of our inventory), one of the playable characters has "relations" with a fellow drug user in his trailer right before killing her boyfriend. As in past GTA games, the playable character is able to go to a strip club as well as patronize prostitutes as well. Needless to say, as a business that caters to families, we don't want this content to be accessed by underage kids during one of our parties.
Thankfully, the vast majority of these otherwise adult-oriented games don't include content meant for more mature users while in Multiplayer mode. For example, in Black Ops III, multiplayer mode is just each player trying to shoot each other, with little if any blood. Zombie mode in Black Ops III is a little more intense but again, no f-bombs and no strippers. Perhaps this makes us prudes; so be it. We strive to make our parties fun for everyone; multiplayer mode enhances the "party" aspect of our events by having our guests interact with each other in a fun, positive way.