system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is your brain so bad at using your non-dominant hand?
gpt
You haven't practiced with it!

With a little bit of time and effort, you should be able to become nearly as proficient with your non-dominant hand... it's just not something most people do.  

As an example, you learned to write with one hand... but if you really hammered away at learning to write with the other hand you would find that (eventually) you'll be nearly as good.