If you don't know anything about any wild berries, beyond some are poisonous, it might be a safe bet to never eat any of them.
If you know something about berries, like this species is definitely poisonous, and this species is definitely safe, and this species you don't know anything about, then it is perfectly safe to avoid the first and third and indulge in the second.
May be because of their unpredictability owing to their jumpiness? That seems very reasonable since humans do instinctually stay away from unpredictable organisms/animals in nature. That unpredictability doesn’t always have to correlate with the real dangerousness of those creatures.
I can’t believe how frequently I have to say this to people: instinct is far from reason.