system
Given the following post, respond as if you're commenting on Reddit:
human
Why do bottles have necks?

Why have bottles come to the shape that they do?  Does the neck serve any purpose other than aesthetics, and what differentiates a "jar" from a "bottle"?
gpt
Practically, it's a lot harder to drink from a jar than from a bottle, same goes for pouring. A bottle is easier to seal as well, using a small cork or somesuch. Jars on the other hand can be used to store thick and/or chunky stuff.