You're moving the goal posts here. The original argument pertained to tanks intentionally not using CDs because they're too focused on their DPS. This makes no sense because using CDs has no impact on your DPS. Not using Shadow Wall or Shelltron isn't going to make your DPS increase. In fact, it's liable to decrease your DPS since you'll inevitably die. Hence why I responded as I did. You cannot abruptly shift the argument to people making bad decisions because parsers. Do that happen? Sure. Is it the majority? No even remotely. You also have to consider what is a "bad" decision, which can be a subjective term. If a Black Mage eats a magic with Manawall to remain in their Leylines, it's better for both them and the raid unless that decision forces the healer to overcompensate.
Regardless, your initial premise: tanks aren't using CDs because ACT exists, is flawed. They're bad because of sheer incompetence, inexperience or some other factor. Not due to a parse.