system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is two weeks notice traditional when quitting? Why not longer/shorter?

My first thought was that it gives the company enough time to replace you but, that seems super arbitrary and not nearly long enough for a skilled position.
gpt
It's long enough for a company to replace you, but also short enough for the employee to wrap up any truly urgent things, say their goobyes, not have to deal with (too much) hostility or coworker retaliation for quitting (if applicable). 

If an employee wants to quit, it's usually because they're not satisfied with their workplace or they found a better position elsewhere (which implies the current position is unsatisfactory in comparison). Dissatisfaction often means reduced productivity, so it's a good thing for an employer to only have to keep them that extra 2 weeks.

Plus, if an employee feels their workplace does deserve more than 2 weeks, nothing prevents them from hinting around beforehand or even working with the employer to ensure a better transition.