Those small wounds they could inflict would build up the more of them there were, and the more attacks they were able to make successfully.
They could pose other problems by just being a distraction or being used as bait for a trap for people to fall into.
People could easily get overconfident when facing them, and that could lead to them making mistakes.
It was the same when there were so many in a much larger number that could create more chaos and confusion.
As they became stronger, such packs could become even more dangerous, especially when they could start inflicting more damage than they were capable of when they were of a much lower grade.
After learning to work as a pack for the sake of survival, it would become second nature to make use of that experience even after they had overcome their weakest state and become stronger.
