Which of the following scenarios may be considered unethical in terms of tipping?

Failing to leave a tip when one is expected may be considered unethical in certain contexts, particularly in service industries where tipping is a common practice. In many cultures, the act of tipping is not merely a gesture of appreciation but an essential part of a service worker's income, augmenting their wages significantly. Service industry professionals often rely on tips to supplement their earnings, especially in establishments where base pay might be low.

When patrons do not tip despite an expectation to do so, it can be perceived as disrespectful to the service provider, undermining the customary practice that supports their livelihood. This can create an environment where the work of waitstaff, bartenders, or other service employees is undervalued, which goes against the social norms established around tipping.

In contrast, factors such as leaving a tip that is less than customary or not tipping due to unsatisfactory service can be seen as subjective measures that take into account the quality of the service received. Similarly, tipping at a fast food restaurant, where tipping may not be customary, does not carry the same ethical implications because patrons do not typically expect to leave a tip in that setting.