In Japan, there is a certain drinking culture with unspoken rules to abide by. And this mainly applies for alcoholic beverages. Most drinks nowadays are single-serve and come in a glass. Everybody orders their own thing, but with Japanese sake like nihonshu and shochu, one must never pour their own drink.
This is probably the second biggest custom in the drinking world. It comes right after the rule of not sipping your drink until everyone in the group has received theirs and made an informal (or formal) cheers.
The world of sake is complex and diverse; there are so many ways to drink a single kind. And tradition plays an important role in the drinking world. If people have always done something, for generations and generations, the chances are that you yourself will be following that same tradition. And the chances are high that you won’t exactly know the origins for these traditions yourself. You only know that everyone else does it, so you must do it too.
Pouring other’s shots for them is one such tradition. It encourages socialization and it keeps the alcohol going. Another aspect to this is that offering to fill another’s glass also helps keep the conversation going when there is a quiet moment. It is the perfect opportunity to squash the crickets.
There are also superstitions behind pouring your own drink. If you are a woman and you do so, you will never get married. And if you are a man, the belief is that you will never advance in your career.
Of course, different levels of formality call for different behaviors. With superiors or in large groups, you will normally be expected to do so, but when out drinking with one close friend, you don’t really have to be so strict and you can stick to pouring your own drinks.