The module usht running the game, the GM is. The module foesnt know who the PCs are, the GM foes. The module doesnt know what the players at that table enjoy, the GM does. Heck, the module rarely runs the NPCs, the GM does.Point is, the module offers none of these things. You just meet a dozen goblin in the jungle, and lose half an hour's worth of playing time.
So, if all the GM does is "lose a half hour" that's his choice, not the modules.