I almost always tip more than 20%, but only because I was a server and bartender for years. Well, I always tipped decent before too. You have to be a real asshole to get less.
20% pretty much is the standard. Sometimes less, especially if the people are old or in their teens. But most nights I averaged out to 19-21%, oftentimes more. And I worked in fucking Missouri if that tells you anything. My personal findings may be skewed though, because the food was outstanding, we had a lot of regulars and of course I was pretty much the best server ever.

Around here, if restaurants raised their prices and took away tipping, the service would be complete shit. It's already borderline shit with tips, and I'm pretty patient with servers. I can only remember two times in the last 5 years I wanted to leave a fucking penny because I was so pissed, and one of those times was at an extremely expensive restaurant where an automatic 21% tip was mandatory and included. WTF is that shit? That lady was a complete bitch, but why should she be pleasant and helpful? She knew it didn't matter how she acted, bitch was gettin' paid. Most people in America are way too fucking lazy to actually be nice and do their customer service job unless commission, tips, or retaliation from their boss are involved. Works great in other countries though.