I don’t want to step in to this discussion (again), but I can’t resist to throw in that “exploration” is an important part of adventure games. There are even (adventure) games that only consists of exploring and where the player don’t know what to do. Examples are Firewatch, Tacoma, Gone Home, The Novelist, etc.
These games work because humans are curious. 
And you find the exploration in MI too: As Lowlevel pointed out, you don’t need to talk to the people in the streets (from the story point of view). But the player is curious who these people are and why they are there. And he is doing things in games, that he will never do in the real world.