Why was fiberboard used as sheathing in the 70's?

[SeattleDIY]

My house was built in 1976. the "sheathing" is black fiberboard. I have heard some refer to it as sound board. I hate this stuff.

Can anyone explain why it was used and when they started and stopped using it??

 

[inspectorD]

It was cheaper than plywood or regular wood and had insulating value.
They did not pay attention to what bugs and vines and water does to it.

It was the newest sliced bread.