I disagree. I tip a dollar per drink no matter what it is. It's no more than 30 seconds of work to pour/ open a beer, maybe 60 seconds for a mixed drink? Then I walk away. Transaction/ service complete. Unlike a server who attends to you for the duration of a meal, while you are also sitting there occupying table space of other paying customers.

Most people run tabs on plastic nowadays, so how's the bartender supposed to even know what they are earning per drink? I prefer to pay in cash & tip dollars as I go, & i find most bartenders are more than happy to get them & continue good service when they see paper coming their way on every transaction.