There is a reason that the server always tries to sell you deserts and appetizers... They want you to buy more and thus give a bigger tip.
Ding ding ding.
Same things with drinks. Servers don't like when you get water, because they are not getting anything for that work.
Part of the reason employers like tipping, if they paid their servers the same base rate, there would be no incentive for them to up-sell.
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