Speaking scientifically, games play a huge role in the formation of traditional behavior and the formation of the personality of any living being with a developed nervous system.
Simply put, kittens, like any beast, it is vital to play: this is how they with peers or parents learn to behave properly, catch up, run away, hunt, calculate their strength and evaluate the possibilities, respect the hierarchy, understand each other and interact in every possible way exactly as is customary for the animals of their species. That is the game are engaged in socializing kids. And still kittens in the course of game get acquainted with other surrounding beings and with environment in General.
A small fluffy mouse can be eaten, and the same small and fluffy ball of wool is suitable only for the game. The big white dog can be dangerous, and the noisy big white fridge is completely harmless.