Yep, 20% is minimum these days. And if you're at a nice cocktail bar, it's customary to do a min 20% tip on your bill rather than a per-drink tip. Also worth noting that the wage paid by employers to waitstaff and bartenders usually disappears into taxes, and wage theft and refusal to pay overtime is common. People often have to give a percentage of their total sales to bussers and barbacks; this is called a tip-out, and it isn't reduced if tips are low. If a server has a really bad day with low tips, they can literally wind up losing money.

To those who don't tip in protest, you're not helping. Employers do not care. If they even notice, they're likely to just assume the server is bad at their job and 'discipline' them, and / or move them to a worse shift where they will earn less. All you're doing is forcing someone to work for you, for free, in a hellscape working environment, so that you can have a nice time. By doing this, you are making someone's life tangibly worse.

I've spent years in the US service industry at all levels; if you've never spent significant time in the industry, however bad you think it is, it's worse. Every job I've held in the hospitality industry has easily been more physically, mentally, and emotionally taxing than any professional role I've had.