The bottles were sold as "drink and food" bottles, but expiring/fermenting food turns the food bottle into a pressure vessel.

I was initially surprised too, because I mostly know Thermos from their coffee/water/etc bottles, but apparently they're also selling these with the intention of storing perishable goods, and in that case a pressure relief system of some kind is a necessity.

Often bottles have special threads with holes in them to let out the pressure when you twist them open, but it appears they didn't do that here.

Well for one, so it doesn’t get recalled after getting a reputation for making people blind

I think most people have the expectation of not getting a cap in the eyes when opening something.

If the safety feature is THAT simple and the lack of thereof literally costs people eyes, why wouldn't that be expectation?!

Because blinding people is bad and causes expensive lawsuits? How is this even a question.

> Why is there an expectation that it should be a required feature?

What point are you trying to make here ?!?!

Given that it should be there, it is quite clearly a product feature on Thermos jars.

So, of many examples that cross my mind.... let's say you were a long-term user of Thermos products. There's your "expectation".

I assume it probably features in the product literature that comes in the box too.