In the USA tipping is expected. The IRS will affix a minimum 8% tip level to server’s income if it feels tips are under-reported. Servers in restaurants have to tip out set percentages to bartenders, hostesses and busboys. So, if you stiff the server, he/she may still have to take 5% of the checks for the shift out of his.her pocket and pay the other workers. Then he/she may get a tax bill for that income not made.
15% went away in the 1980s. 20-25% of the pre tax bill is a proper tip in 2018. If you cannot afford to tip, go to a joint without table service, you don’t have to stay home. BUT, if you have service pay for it.
Similarly, push your state legislators to raise servers’ minimum wage to the same as everyone else and get rid of tipping altogether.