The customer/server relationship is one of the more messed up dynamics that we take for granted. We walk into a restaurant and expect some random underpaid person to cater our every need so they can actually get decent wages. It's a crazy system.
While we should always try and tip properly, the brutality of tipping culture is only one side of the coin. The lengths some wait staff have to go to so they secure these tips are a lot, even if they aren't always dealing with the very worst types of customers.
This has been underlined in a frustrating Reddit thread, in which those working in restaurants ponder 'the psychology of dining out'. Reasoning that there is something about the whole process that turns diners into 'a confused child or a power hungry tyrant', it's an enlightening read. Even those of us who try and be nice to servers are probably guilty of some of these annoying little tics.