Why is 12 so important?
The first number, 1, is about starting things, independence, and exploration. Separating from all-ness is an astounding experience.
The second number, 2, is about cooperation, teamwork, and relationships. Following the first experience of separation, existing with another is welcome indeed.
Those are the first two experiences.
When those two experiences are put together, the third experience is manifested (1+2=3). The number 3 is about creativity, social interaction, and communication. It is a natural outgrowth of the first two experiences.
12 is the foundation of the first triad, the number 3.