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

Why? Well, if you're a valuable employee your boss would really like to know ahead of time so your departure can be planned for.If you're valuable enough then it would be even better to give as much advance notice as possible. That is, if you want to remain on good terms.

If you don't care about that, or if you were a shitty employee anyway, then you can just walk whenever and it won't matter.

If your company has to do lots of layoffs, the chances are that people know it is coming anyway and lots of money is at stake. The company's primary loyalty is to investors, not to employees. Often severance will be involved anyway.

Finally, if you're a true frickup then they can and will fire you on the spot.