I can afford to tip, but nobody has presented a reasonable argument as to why a $15/hr person deserves to be tipped.
What about giving bonuses to a salaried employee in circumstances in which an employment contract does not mandate bonuses, commissions, etc.? I'm sure that all salaried employees would appreciate receiving a discretionary bonus.
So why should a salaried employee receive a bonus when their salary works out to an hourly rate in excess of $30 or $50/hour? It is an incentive to perform to peak capacity. It is an incentive to be attentive, to help drive customer satisfaction, to encourage repeat customers.
Tips should be (and, to me, are) used to incentivize prompt service. At some restaurants we frequent, the waiters literally argue over us or, if we sit in another waiter's section, they ask to switch tables (sometimes two for one) in order to ensure that they will be serving us. They are hyper attentive and go the extra mile to make the dining experience pleasant - from remembering our drinks and orders, to providing us with complementary o'dourves. I value the experience, and they value the appreciation that I show them.
Granted, you may be able to argue that getting shitty service should result in them getting fired, and that the service should be "good" for all patrons. In such circumstances, the tip is there to ensure that you are prioritized higher than other tables during rush times, that your order finds its way to the line faster than other tables, etc.
I thought I remembered someone saying that Ns1 was broke and always bitches about not having money or nice things. And here you are complaining about spending money on a tip.