What stays out where people can see it. A butter dish that holds butter at the temperature where it spreads rather than tears the bread, and a jar that actually seals, because a jar that does not is a decoration with biscuits in it.
Both are meant to be looked at. Neither is meant to be hidden in a cupboard.
These two pieces are doing the same kind of work and pulling against each other while they do it. The cookie jar is keeping moisture out, because anything crisp will pull water from a room until it matches it. The butter dish is keeping light and air off, because butter does not spoil so much as oxidise, and light is what drives that.
That is why one has a silicone gasket and the other does not need one. A butter dish that sealed airtight would sweat. A cookie jar that merely covered would be a bowl with a hat on.
A cupboard is where good things go to be forgotten. Butter in the fridge is butter you will not use, and biscuits in a tin at the back are biscuits nobody eats until they are soft. Both of these are built to hold their contents at the state you want and to be worth the counter space they take, which is a design constraint as real as any dimension.
The detail behind each: how long butter can sit out, and why cookies go hard and crisp ones go soft in the same jar.
