Why does leprechaun kill for his gold?

A leprechaun kills for his gold to survive. If a leprechaun does not kill for his gold he will become very weak and eventually die of leprechaunitis (a horrible disease were the leprechaun turns human and explodes). A benefit to this barbaric nature is that when a leprechaun kills a human he gets another pot of gold at the end of his rainbow.

The myth goes that if you defend yourself against a leprechaun and kill him, he along with his gold will disappear. If you do not kill him and kick him in the crotch he is forced to hand over all his gold. Regardless of the outcome the leprechaun will get leprechaunitis and die. If you want to avoid this outcome then do not go anywhere near an Irish lake, Irish rainbows, forests and do not say "Ghoid tú mo cáca milis" or "Ghlac mé saighead chun na glúine".