Tip is an additional payment made to workers in order to appreciate their service. The tip is in addition to price of the product or service purchased. These payments are part of the social culture. In some of the culture not giving a tip is considered a serious voilation of accepted social norms. It can be even be considered as very miserable and unethical. On the other side there are business where receiving a tip is illegal. Also, there are places where the tip is usually not offered thus providing a tip is considered as exceptionally good behavior. In world there is a mix of treatments for the tip however very few place (or situations) are there where it is mandatory legal requirements
In cultures where tipping is a norm the drawbacks could be that the employers may pay less to the workers assuming that the tip will make up the difference. Such conditions can put workers under trouble as they may not receive appropriate remuneration floating in industry.
If there are service charge is applied on the bill then the tip may not be expected
Different countries have different conventions for tipping. It can vary from no tip to obligation.