Creating lots of poses my self, the answer is a clear yes :D

On a more serious note, I see a lot of benefits in doing so and not really a lot against. Obviously it depends on what you are trying to achieve or make. If you just need to render an image once in awhile, it's probably not worth it.

But for me personally, I like creating comics or stories, which need a lot of frames and pages to tell them. So having to create one pose after another takes a very long time and on top of that you still have to make all the other stuff in the scene as well. So being able to save some time using premade poses save you a lot of time.

At least the way I work, and I mostly use my own poses now, since the whole library is around 600+ unique poses, so have quite a few to choose from. Funny enough though, despite having so many, I actually rarely use them directly as I created them, but will find the pose that matches what fits the best and then Ill adjust it, and even using them like that, is so much faster than having to make them from scratch.

To make a pose for me from start until I save it to the library, can take between 15-45 minutes and even longer if its couple pose. Personally I enjoy making poses, but when im in the mood for making a story, I really don't want to have spending to much time on it and just want to get the story moving along.

So to me its not really any different than buying a piece of clothing, you could spend the time making your own, but in some cases, its just nice not having to worry about it and just get things moving.

In the end for me its about saving time and having fun and the faster you can get to the end result of what you are imagining the better, I think.