Ye that's something which have been discussed a lot if you look at all the other commentaries. I've explained that at the time, since I knew that a lot of devs work differently for animation (frame folders, spritesheet, etc), I've decided to export it like that since it's easier for devs to make a spritesheet/atlas with frame folders, following their preferences, instead of asking to devs who want to make frame folders to find a way to do it with spritesheet/atlas.
For the next ones, I'm planning to simply export into different formats in advance. But I know that even if I do it, some devs would tell me that my spritesheet is not done like the one they want (for example some devs prefers spritesheet per animation, some others prefer a single resolution for all animations instead of other prefering a different resolution per animation/spritesheet, etc).
So in the end I'm up to ideas but for now frame folders seems like the best choice to let people do what they want :)