We have a bunch of milestones within easy reach, basically. We want to push ourselves up to level 5 in a few places and level 10 on the beam because we're expecting to unlock bonuses for doing so.
I don't see any reason to wait for combat to do that, as it's almost certainly going to be the best path, and because, let's face it, we might well get thrown into combat without getting the opportunity to spend it, due to a surprise attack or similar.
Also, if we unlock something good we can train with it.