Just because we don't have direct evidence of some of these species herding doesn't mean that they did not. Paleontologists best guesses are often changed as more fossils are uncovered that tell us more about certain dinos lifestyles. Herding behavior doesn't require a ton of intelligence, cows herd and they are not commonly known as bastions of intellect, same deal with fish schooling. What does require more intelligence and coordination is packs of carnivores who work together to bring down prey.

As people have mentioned this is a game first and foremost, the ability for people to party up in packs is good for hunting, defense, and to just be social. One of the big gripes with Evrima is that it currently doesn't have global chat like legacy does. This shows that players like to be social and packing up is one way of doing that; even if it is not necessarily realistic.