[so cal lurker]

Originally Posted by AremRed

I noticed that the other day, why is that? Is it for the scorer who usually sits behind?

Scorer shouldn't care as would be tracking as each pitch happens.
I doubt you will find The Reason for this as it's been that way for a very long time. But I'll bet you can find a lot of theories. E.g., since strikes are signaled with the right hand, it makes sense to show them in that hand.

But since it is two separate things, not a two digit number, there may be no rhyme or reason.