re: Why do you have(traditionally) to give a two weeks notice, but your company can

No. They can tell you to get fricked and have the police escort you out and mail you your personal shite and not pay your for a minute past the time you said you were done.

You don't have to work for them, they don't have to employ you (unless you're a protected minority or they're scared of a wrongful termination suit, but we won't go there)

When you work hard for good people and maintain a good relationship with them, both parties try to do right.

When your employer sucks and you have a legitimate reason to just leave, do it.