system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: If you're not supposed to ever button up the lowest button of a suit, why do they exist?

Fashion dictates that men never button the second button of a 2-button-suit or the third button of a 3-button-suit. Then why are they there? If it's just for "style", why not have the button, but no hole?
gpt
It's a silly reason, really.

Originally, jackets were *supposed* to be done up all the way. But at some point, people decided it looked better if they 'flared out' around your waist (since this was typically the widest part of the body... at least if you're a wealthy over-indulgent Earl). Having the fabric pulled in around you could look silly, and so they stopped buttoning it up.

Since then, manufacturers have started tailoring jackets to intentionally take this into account, *but they never removed the button*. [EDIT] As some other commenters have remarked, it is like a vestigial remnant of times gone by.