The difference is real life has immeasurably more entropy and variance and randomness. Fiction is created, with intention, and good open world game design is one that leads and pushes and hints at things, preferably without being explicit - unless this explicitness is itself (mis)leading you somewhere or is just the McGuffin of the story.

Fiction without intention, even in its smaller, seemingly random encounters and details, is just messy and disrespects your time.