Unfortunately a lot of people have a herd mentality.

Here's a funny hypothesis for you to enjoy:

All energy comes from God, and is connected to God, but once it is cast in to the crucible of the material world it can be separated and purified and returned to source at the end of the process. (aka good people go to heaven).

However, there are now so many people God has to start promoting lower forms of energy before it's evolved over a long time, so now we get people ensouled with energy that was previously used to animate lower life forms, such as dogs and cats, but also lots of other less intelligent creatures, such as deer and lemmings.

This is why some people are 'old souls' and appear to be born with innate knowledge and understanding, whereas others seem newborn and have characteristics of the animals that their energy was previously used for.

Now, in the animal kingdom, it's a food pyramid, there are a lot more prey animals than predators, so it stands to reason the greater proportion of newly ensouled people have prey animal energy, and prey animals herd together for safety because they lived their lives in fear of the predators.

It may not be true, but it certainly explains a lot ;)