Why does it seem that most places you buy alcohol/beer from ...the people who sell it seem "obnoxious"?

Imagine from their perspective. They have a boring job doing the same task more or less repeatedly, the people they are serving are often drunk ******* who think they're funny. It must be tiresome. They also get abuse off underage people who they catch trying to illegally obtain booze. Then to top it all off - you know how when we're at work a lot of us are wishing we were out/at home with friends having a nice drink and a good time, well not only that but they are having this literally rubbed in their faces as everyone is having a good time around them but they are having to clean stuff and serve people. Also they know at the end of the shift they will no doubt be cleaning random people's puke from various areas of the store. I'd be surly too!