What are some "legitimate" reason for a citizens to own firearms with high-volume clips?

This is not intended to be a “poke” at gun-lovers. I am asking because I truly do not understand the need or desire for high volume, high speed clips in a peaceful society. I understand and support the rights of sportsmen, recreational shooters, and the like, and I grew up in a rural area, and had a b-b gun, and as an adult I have lived in several rural areas where having a sidearm or shotgun handy might mean the difference between being bitten by a poisonous snake or not.

That being said, I fail to understand the need (as opposed to the want or desire) for a high-volume firearms, except by police or military, for obvious reasons. Can the collective enlighten me?