This is mainly a problem with obsidian because it takes so long to break. If you break obsidian with an Efficiency pickaxe or Haste level or combination which can instamine netherrack, you can't see the obsidian's breaking texture, which gives you no clue of when it will break. This results in you involuntarily instamining all of the netherrack behind it in your line of sight which can cause the lava to escape, potentially killing you. Even with brightness up all the way it is difficult to see the animation.
I think the color of it is intended to be dark, but the fact that it makes it almost impossible to see the breaking animation texture for some blocks is an oversight.