Because Berserker is overpowered and awesome. This is a random compilation of what happens when we introduce the giant rage-machine that is Berserker-Heracles into various other worlds. I blame Zelretch.
IntroductionThe mighty being known by the name Berserker is a noble and valiant being. The summoned existence of the great hero Heracles, he was drawn into the world as a weapon and protector. Heracles was known for his great heroics, ability to accomplish the impossible, unbelievable strength, a love of women and wine, and the occasional slip into bouts of insane violence. He always meant well, of course.
The body he was granted was perfect; it further enhanced his already absurd strength, made him faster, and all but immune to damage. And, if the worst should happen, he had a backstock of lives to resurrect himself.
He would faithfully protect his summoner, he would carry out their will, he would be a hero again!
It wasn't his fault that his body only came with two behavior modes.