I hold the view that being generous is good, but equally that it is nigh-on impossible to be generous without also conferring a benefit to the self. Quite simply, being generous makes us feel good, so all acts of generosity are at least in some part self-beneficial too.
Tipping is a social convention whereby in most cases one's generosity aids lower paid workers. But tipping also encourages a better relationship between service provider and customer, and it incentivises a better service too. This varies, though, according to the service. When we tip taxi drivers we pay into an optimisation ethos which encourages every customer to give a tip and encourages every taxi driver to deliver a good service. I suppose a good service for a taxi driver is turning up on time, not taking a circuitous route, and being friendly and chatty. Given that we expect the first two as being integral to the service, I suspect the tip variance is mostly to do with the personality of the taxi driver. I feel more compelled to tip a friendly talkative taxi driver than I do a terse grumpy one.
When it comes to waiters and waitresses I think things are different. Tips for waiters seem to be part of a social custom that increases their low wages to a more decent level. I'm not sure that is as bad as many people claim. A tipping system helps restaurant owners employ good staff - the more reliant a waiter is on his or her tips the greater the incentive staff have to be friendly and proficient. If wages were higher then prices would be higher too. Lower wages and tips means lower food prices and the same wages for waitresses. An optional tip service incentivises friendliness and proficiency, and leaves it to the customers' discretion whether or not they want to contribute to the wages of the staff. Price-sensitivity is a factor too. With tipping policies more generous customers pay more for their meal by leaving a tip than stingy customers do by not leaving a tip.
But whichever way we cut the cloth, there is little rhyme or reason to it. There are many low wage workers that we do not tip due to a lack of social custom. And similarly there are people who earn more than us that we still tip due to social custom. We don't tip staff behind an information reception desk, nor the till operator in Sainsbury's even though many of them earn the same sort of money as hairdressers and window cleaners whom we do tip. Conversely, a taxi driver probably earns more per hour than many of his low wage tipping customers, and a painter or builder is often tipped by clients less well off than himself.
Clearly a big factor in tipping is service and intimacy. The relationship a client develops with a builder working on his kitchen for three days may be sufficient to make him feel compelled to offer a tip. On the other hand, a McDonald's worker who earns less than your builder probably won't get a tip on the basis that they only spend a minute serving you.
In restaurants it is often the case that tips do not go to the individual waiting on you but into a collective tip jar that's shared out at the end of the week (this is classed as taxable income in the UK by the way). Is this a better policy than each individual keeping their own tips? Mostly yes. Although there is one obvious exception. When tips are pooled there is less incentive for Lazy Larry to work super hard and be super polite. If he under-performs he can still be carried by Diligent Dave and Hard-working Helen, and reap a proportion of the total tips collected. But aside from that, it seems that the policy of sharing out tips works best, because it means the bar staff, and staff behind the scenes receive a share too and are not penalised for not dealing with the customers directly, despite working just as hard and being on similarly low wages.
Lastly, I've considered that tipping is a sign of generosity which confers benefits on the self - and that this is probably primary over our desire to help low earners. To see why that might be the case, consider this hypothetical scenario. You're on holiday in
The upshot is, the world of tipping is built on social protocols and on conferring pleasure on the self by distilling pleasure from being generous. It is not all about helping low paid workers, because there are a lot of low paid workers that is it not customary to tip. It is not all about performance, because we tip people even when they have under-performed. It is much to do with the good that comes from generosity and the rapport developed between clients and service providers over a sustained working period.
Just a closing thought: if being deserving of a tip is predicated on a sustained short-term relationship, low pay and (in addition) importance of the service to you, then perhaps nurses and firemen are good candidates for tipping.