alt Hacker News> 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.
> Given that it should be there
I've never seen a thermos-style container with a pressure relief in my life. However, I'm European, it appears that in the US (a country where you have to write disclaimers on microwaves that you shouldn't dry hamsters in them) common sense has been going down the toilet.
Frankly, I'm all for a bit of darwinism here. It's bewildering that there are people who think it's a good idea to open a thermos that has been fermenting for days if not weeks without a lot of caution!