Why should I give a two weeks notice?

There are no other advantages for you other than the ones you've listed.

Giving two weeks notice is important because that covers typically all the shifts that you have scheduled and gives them time to make sure that your shifts are covered by someone else. Could you run a business if your employees just quit and you didn't have time to find someone else to work? It's just good courtesy and it's the right thing to do.

You are aware that two weeks notice to an employer i.e. is professional courtesy, use job as a future reference, give opportunity to employer to train someone on your position, and many employees want the two weeks pay without interruption in salary since there is usually a delay depending upon when you start the new job in receiving your salary, never know if the boss you worked for will turn up at the new place you are working (which happened to me) since my former employer merged with my new employer (now one organization) etc.. It is always about not burning any bridges which you will regret later coming back to bite you we call it career suicide.

Very simply, it is professional. It is just understood that you should give that much time for the company to plan for your departure. Additionally, prospective employers can and will ask you if you have ever left a job and given less than two weeks. It can mark you as a bad potential employee or result in burning a bridge. Even if you don't like that job, don't want to go back, and would never ask anyone there for a reference, you should always err on the side of professionalism and tact. It will get you farther.

If you give two weeks they will let you come back.

How would you feel if you have a business yourself and an employee you were relying on simply disappeared without any notice? You seem a tad immature if you actually need to ask this question

It is a two way street .. they have to give you two weeks notice to terminate your employment so you have to give them the same .