The one gun concept is based on legal restrictions, means or needed uses.

A person without wealth can't afford endless frivolous new purchases.

A person who only hunts deer and boar can get by with one medium calibre rifle.

A person only hunting rabbits hares and birds can get by with a .22 RF

A man hunting in Africa can cope with just a .375.

A .375 will damage meat more than a medium calibre so that is a consideration.

I exempt the need for a shotgun from a one rifle hunter concept.

But I do admire persons who limit themselves to a rifle or a number of rifles and know them like the back of their hand.