There is a big difference between drinking a beer and tasting a beer professionally. While drinking a beer, the focus is on quenching thirst and enjoyment. Whether a person enjoys a particular beer is a matter of personal taste and circumstances. In a busy noisy pub together with friends at the bar, it basically matters less which beer one drinks. The social interaction takes precedence over the quality and taste of the beer. In a specialised beer pub, one goes in search of a specific beer with a particular flavour. Enjoying the beer is paramount.
While professionally tasting a beer, it comes down to describing the beer objectively without personal value judgements. This requires, knowledge, training and experience.