It’s the humidity in tropical regions. If it’s not sealed properly, your biscuits will absorb the moisture in the air and turn soft. They’re not oxygen removers, they’re water vapour removers and it’s there for a reason. It’s not because we hate the environment or we’re nuts. Hell, English as far as I know doesn’t even have a word in common usage for it. In Hokkien we have a word “lau hong” which literally means to lose air as in lose the crispness of the biscuit. Hell, there’s also so many ants here that when I was in Finland, I was shocked that people leave biscuits as is without putting them into containers. If you do it in South East Asia, your biscuits would have become an ant colony in hours.