I have never worked as a server, but my daughter has. I've also known many servers and have been close friends. I have always considered that line of work as contractors to the restaurant with a few exceptions. Most don't have benefits such as insurance and 401k accounts. They make a minimal amount from the restaurant for their idle time to help the cleanup staff and to make sure their area (tables) are presentable. They sometimes share their tips with other wait staff and bartenders to help them do their job. I see that their main objective should be to service their customer, not to work for the restaurant. If they are doing their job, then I should get the right food I ordered at the right time and in good condition. I shouldn't have to send anything back, they should inspect the product and refuse it for their customer at the kitchen. I was once served bacon that was burnt, it was black, totally inedible. Wait, the cook saw it, whoever plated it saw it, and at the minimum the server saw it. That bacon should have never come to the table. Anyway, I consider servers as independent contractors providing a service, not a product. If I pay $15 for dinner, then I expect good service, but those servers are not at the level that a server would make at a $300 per person restaurant. I was at a $120 per person restaurant, and the server took the order of 15 people without writing anything down. And he got it perfect. And he actually served the food making sure everyone was happy. At a $15 restaurant, I'm lucky if I see my server and they never bring out the food, it's always someone else that has time and just drops it on the table. If I ask for anything, they always say... "I'll get your server".
Yesterday I stopped in for a beer, the service was outstanding, the beer was okay. The server made sure there were no water spots on my glass, when she filled the glass, she rinsed the outside of it, and dried it. She took time to explain their beers and I saw this for every customer that was there. I didn't tip on the beer, I tipped on the service... it came out to about 34%.
I will always be an advocate for tipping, but if it's a requirement, I don't tip above that. I let the server know. I personally know many people who do not tip, and I have also gone back to the table and added to the tip, when other people offer to pay the bill.