It’s potentially important when it comes to framing the shot as well as useful to making your action hero look taller, and therefore more menacing.
However, in Kong: Skull Island the movie wanted Samuel L. Jackson to look bigger than he was, but Jackson decided he needed to look even bigger than that.
It’s far from uncommon for actors to end up using boxes or other objects in scenes, but frequently, it’s because they’re trying to make one actor not appear too short.