There are three true gods in the world: Order, Chaos and Nature. All of them patron a couple of humanoid races that carry their values. While Order and Chaos carry on their petty feud fought by their petty races (humans and monsters), Nature only care for one thing in its creatures (elves): evolution.
Evolution demands quantity. If not enough individuals are born, there is not enough mutations to select, thus Nature's creatures are prolific. Evolution also demands pressure to direct the changes, otherwise there will only be diversity, not improvement, thus Nature's creatures also die in decent numbers, both in order to select the good traits and to prevent overpopulation from destroying their habitats.
One of these selection mechanisms is their child rearing method: "let the kids play". Elves are not as protective of their offspring as other races (except against infanticide). Elven children play outside with little to no supervision and, as not all children are able to fight off or outrun bears (unless they are in a gang), a reasonable amount of them die.
As the less fit kids are the ones that will usually die, the overall fitness of that particular specie increases. However, the "hazardous playtime" gene brings no direct benefit and quite a few disadvantages, while the "I want mommy!" gene increases overall survivability without providing a meaningful disadvantage, thus being likely selected. This cannot happen because little elves running wild in the forest is just to good to not happen, thus arises the question: how can dangerous behavior starting when they are toddlers increase individual fitness? Or how could this dangerous behavior be more or as advantageous as staying safe?
- the problem is not "how could this evolve?", the world has enough divine intervention, but "how could this not unevolve?". Even if those imps are just that punk, I can't think in a single advantage in picking fights with wolves, as opposed to staying safe at home where there are no wolves or bears.
- elves are magical, but I would rather not make them magically inclined to suicide with extra steps. More over, Nature is darwinistic, it cares for results and overall fitness, not the process and individual adaptations.
- elves toddlers are way more independent than human toddlers, and depending on the particular specie they are more capable of defending themselves than most adult humans.
- This is not the only child rearing method across all elven kind, there is a lot of elven races, some of with employ this method as the primary
- elven toddlers are adorable and adorably vicious, they go home to feed and sleep most of the time, but when its playtime they gang with their friends and go do dumb childish stuff, usually involving tormenting their neighbors or local wild life.
Edit: examples of dumb dangerous behavior practiced by little elves.
- Playing "hunt" (approaching furtively and attacking with sticks and bites) against big herbivores, wolves, bears and other elves.
- Playing "war": an bunch of children beating each other until one team surrenders or flee.
- Playing "hold still, I want to try a thing I saw two drunkards doing in a bar", and the thing involves knives and one or more children.
- "So what it will take us the whole night to get home? Its not like we are some dumbasses that would get lost", said the dumbasses.
- "Whoa, a step cliff! I want to climb it!", said the toddler about to climb a steep cliff of bare wet rocks next to his friend.
- Trying to stone his friend, who is climbing a steep cliff 30 meters above the ground.
- Literally trying to get something to attack him, like pulling the tail of a sleeping lion
- -"Wait, is that a dragon? Lets go there to check"