I remembered this wasn't really an argument thread, so I'll just dump my perspective here, however out-of-context it might be; I don't know how prolific open SBs are on Guild: 

Sandbox roleplays are the antithesis of roleplaying in-general. You can't have a roleplay rely on individual story arcs and it still have the RP title. There's no [i]delicate balance[/i] for a GM to uphold between holding players' hands and providing no direction. Literally, all a GM provides "direction-wise" in the first place is a setting. Nothing beyond that is up for them to control. They could tell a player to write [i]their[/i] story how they'd [i]personally[/i] want them too. Ultimately, people need the courage to create their own narratives independent of other people, so we don't end up with subforums full of damned roleplays because the players don't have an author's grit; they can't keep an independent project alive, how could they do the same for someone else's??