I would be embarrassed to not leave a tip, unless the service or the food was very bad.
I know what you mean, but I wonder where we came to a point where we're so heavily socialised to add extra money UNLESS our experience was significantly worse than OK but nothing special. Somebody upthread used the phrase 'stingey tippers', as if it's somehow shameful to agree a price for something and then not to pay significantly extra when it's supplied.
Do most people in regular employment look at their payslip each month, see that it's the same as last month (i.e. one twelfth of your salary minus stoppages) and criticise their 'stingey' bosses, as if it's a surprise?
If you spent £20 in a shop and handed over a £20 note, you'd never expect the assistant to think you stingey for not adding any extra money. Even if you spent £19.99, nobody would consider you tight for taking your penny change.
I'm not saying that waiter/esses don't work hard for their money, but, as has been said, so do lots of people - carers especially.
Also, if we are tipping, I don't understand why it's done as a percentage and not a standard extra fee. Why is it worth more to bring a lobster to the table than a salad? Amazon couriers don't get paid more for delivering a box containing a laptop than they do for one containing a multipack of toilet rolls.
I detest it when some websites clearly aimed at domestic customers (I know it's different for business customers) will give prices for everything and then, once you go to your basket and check out, add VAT on top of the total price it's given you up to that point. I have been known to abandon my purchase for that very reason. How is this scenario any different really? In fact, it's worse: I can abandon my basket of goods and halt the transaction online, but I can hardly give back the food I've already eaten.