system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How come our non-dominant hand is less capable than our dominant hand? Why isn’t everyone ambidextrous?
gpt
You get more specialized in that certain hand, that's why.

Let's play a game:
We have two characters Leftie and Ambie
Ambie does everything with two hands equally dominant. So she prefers going one right, one left at all times.
Leftie only does left hand.

Let's give them a task with a reward
Task reward: 1 experience points
You get a level up at each 5 experience points.

Ambie does it 10 times. She gains 5 experience for her left hand, and 5 experience for her right.
Her both hands are lvl 2 now.

Leftie does the task also 10 times, only with left hand.
He gains 10 points for the left hand, while right gets nothing.
Left hand is lvl 3 now, while right, he uses it for other purposes.

Leftie is better at this task than Ambie now, due to his focused experience.

Now imagine if you were an artist, or a surgeon, or any other skill based worker.

You can see the advantage. Hope it helped!