It is in my case. I've only done difficult content up to ARR EX primals synced where Dissipate is not available. But that isn't the reason why I don't bring it up. The reason I don't is because while only a percentage of players participate in EX/savage content, everyone runs casual content. But I do admit, I would likely be more inclined to bring it up if I participated.
While true, the potential of fairy swaps is lost due to the fact that they share cooldowns, and it is one of my gripes about the job. I am also not sure if you are referring to using Dissipate as a means to fairy swap. I tend to think of fairy swaps as immediate, and after a 30sec cooldown, it is simply a summon or re-summon.
The long cast time of fairy swaps is also troublesome. Burning up swiftcast, or losing gcds due to the cast time is hardly ideal. The most ideal situation I've found is during phase changes. One fight that comes to mind is The Aery version of Niddy. I use Eos in the beginning, and summon Selene when he leaves the arena signifying the add phase in order to get Fey Wind on everyone, which ends the phase quickly. When Estinien raises the shield, I re-summon Eos. The reason why I bring up this instance despite still not having Dissipate is to show that the most ideal situation I can think of doesn't require the skill, and it requires that I immediately summon another fairy, which Dissipate takes away.
Dissipate in this same situation would have me sacrifice Fey Wind in favor of increased stacks and healing potency, but since pushing this phase as quickly as possible is the best way to mitigate the damage Estinien takes, Dissipate would be the less ideal choice. I'm guessing the same rings true if similar mechanics exist in endgame, but correct me if I am wrong. Fairy swapping isn't required to push the phase I mentioned, but it sure in hell makes it a lot easier. Perhaps in endgame, these DPS windows are smaller and far more helpful to do.