Tipping is ingrained into our basic economic culture. Restaurant staff (waiters and waitresses in particular) make 80%+ of their money through tips. Federal minimum wage is about $7.25 USD, and almost no states have a minimum wage that low (some places it’s easily double that), but it’s completely legal to pay wait staff $2.25 an hour and expect them to make up the difference to $15-20 per hour in tips almost anywhere. A standard “good” tip at a restaurant is 20%. Even going to a grocery store you’ll often see a tip jar on the counter that people toss their spare change into. Outside of restaurants, no other job is completely dependent on tips to live, but in many service industries it’s still customary to tip as a way to show appreciation for a service rendered (especially if they go above and beyond).