It's important because it means you value your customers and you value giving them the best service with the least hassle and red-tape. Good work ethic also means that you are more likely to put more effort into making your workplace a better place; you are interested in making your boss happy with good, efficient, cheerful work; and that you are honest and trustworthy. A good work ethic is especially important for when you want to get a new job; you don't want to have a bad reputation, since this will jeopardize your chances of being employed again.