CMV: Those who work in professions w/ tipping should not expect tips.

I hear time and time again from friends, coworkers, and associates how upset they are when someone doesn't tip well. Or when people don't tip 15%.

I have zero issue with tipping, and often do, especially if enjoyed my interaction/time.

The only issue I have is that people feel like they are owed a 20% gratuity for simply serving you and doing their job to the bare minimum, is a tip not a extraneous recognition of excellent service? Should I tip for mediocrity? If the waitstaff was slow, hard to find, and unapologetic?

#EDIT: I forgot to mention I have only ever lived in California, so some of the wage regulations are different. And while I am not fully versed on them, it appears to be $9 an hour + tips

Please; change my view.