Every Thanksgiving I wonder why green olives come in jars and black olives come in cans. This is generally an issue I mutter about while trying to find something to contain the leftover black ones. Then I forget about it until next year.
But hey. This is why God made Google. I started typing and the suggested search popped up before I'd finished, so apparently inquiring minds want to know.
Long story short, green olives are brined raw and packed cold. Black olives are processed differently and have to be cooked in the can. Glass cannot withstand the required temperatures.
So now we know. Ain't the Interwebs great?