Tom, from what I can tell it comes from the notion that "since it was done to me I need to do it to the next person". While I've never personally experienced it I guarantee you I have enough knowledge to work off of here
It's tough for old fart alums to come into their old chapter and change things because they NEED to be changed. It's even tougher to get those old fart alums convinced that things should be different from when they pledged in 1960.
Changing an organization's culture does not happen overnight. It takes a lot. Sometimes even forcing a chapter dormant so you can start with a fresh crop of new members without the traditions that previously held the organization back.
If HQ's don't look out for those that are hazing they will be sued out of existance.