(1)
If you only need to reset the skeleton after every animation so that it plays back in-game the way it does in the editor, you need to use is setToSetupPose at runtime (see Nate's link for the explanation). The Spine runtime doesn't make the assumption that this is the behavior you want in the animation system because you may also want to do some complex animation mixing and things (like in 3D games).
(2)
But for setting up some pose-to-pose animation (and for other generally-useful things like holding a pose), a key-all-keyed-timelines shortcut/button would still be an indispensable part of workflow while still making sense in the context of Spine's animation system.
The lack of such a feature makes most animators assume the best way to go is just to key everything manually so they know things will stay put where this is done. You can't really blame non-programming animators for not being aware of its effects though. The bad thing is that, after this sort of "damage" is done, it's currently such a pain to remove useless timelines 'cause you have to check almost all the timelines and keys to see if it does anything and make guesses as to whether they're actually useful for the animation or if they were just a result of (copy-pasted) key-all-SRTs.
As Nate explained, this gets really inefficient and can bog down your game, especially if you have enough copies of them in one game scene.
The Key-all-keyed timelines feature is already in the list though: Key all keyed timelines.
