Near where I live there is a bakery/cafe/bar hybrid that has all tables being 3 tables for 2 people joined side by side. When it is full, frequently it happens

Near where I live there is a bakery/cafe/bar hybrid that has all tables being 3 tables for 2 people joined side by side. When it is full, frequently it happens that if there is two people on one set of 6, the other 4 places are empty (does not matter where the two people are). Except when the staff bother separating the tables by a inch or two, then all tables get used, it is a really curious effect.