There are two answers to this. First, you will not have the job very long. Most unethical businesses are found out, and go out of business. In recent years in our community we have seen used car dealers who turned back odometers closed down, medical companies who inflated bills forced into bankruptcy and dishonest car repair shops put out of business. An unethical person might feel comfortable in such a business, and even make money for a while before failing.
Unethical behavior works only in the short term.
Ethics sells, because ethics means success. If an employer knows that you will treat customers with respect, take responsibility for your actions and be honest in your dealings, that business will hire you, whether you have any other skills or not. Time and again human resource officers say it is easier to train people in business skills if they already have ethics skills. You are building your future A person might make a lot of money for a short time by being unethical. Many people, including those who have never developed the skills of ethics, may be tempted by this opportunity.