Good discussion on why adv/disadv not in the dice--it's in the impact of the decisions.
Say player wants to climb a steep wall to get to the top.
He can climb by hand. If he fails, he falls to his death.
He can climb using a grappling hook and rope. If he fails, he gets jarred by a brief slip and loses a bit of gear but is able to continue the climb to the top.
The consequences of his approach, the decision he made, impact the outcome, which amounts to gaining and advantage from using the grappling hook.
Mechanics are the same/similar but the consequences might be much better (adv) or worse (disadv) based on how smart or dumb you approach the obstacle. So a fail on a hand climb, you may fall to your death; a fail on a grappling hook climb may be you slip a few feet, jarring your pack and losing an item. Your approach matters, the fiction matters, the consequences of failure should be the difference and reflect how well or poorly you approached the problem.