Why different thickness between 2 sticks?

Hi, guys:

I'm still new in playing drum,

but I've got more than a decade of pairs of drumsticks in my bag.



I found there's always a difference in thickness between 2 sticks of a pair.



Is it normal to drumsticks?

Or the drumstick companies do this on purpose

, like the thick one for weaker hand, the thin one for strong hand ...etc.?





Thank you :)

Why different thickness between 2 sticks?