[Gustoo]

Well..it doesn't matter why. They're classic.

But yeah it was to balance the fact that the class could take hits and use spells which was kinda the best. (In theory)

Also people didn't really know much about these penalties.

Ogre and troll cuz they so dumb
Halfling cuz they so cool

But they say the halfling bonus was supposed to be a human bonus (cuz they so basic) but I'm glad it is the way it is.