Tipping culture used to be a courtesy, but now it’s been classified as part of salary so restaurants don’t have to pay minimum wage to their waitstaff. You’re not required by law to tip, but depending on the place, waitstaff will remember if you tip or not and how much.
Tipping has not gone away except in some places where they explicitly say it’s not necessary.
Typically I double the tax amount and leave that as the tip. I will also round up from there if it’s an uneven amount to reduce change. Finally, I’ll pay more if service is exceptional or I’m being served by someone I know personally or if they’re doing me a favor.
Some places include tips in the bill, so be careful. I also usually don’t tip if picking up food because there is usually no guarantee that my tip would actually go to the people who actually prepared my order.
I also tip other service jobs (Barbers, mechanics, plumbers, etc..)