system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 Why are teenagers often played by actors who are in their twenties?

I just started streaming Netflix and have noticed that a lot of teenage characters are played by people who are 6-8 years older.  Break it down for me.

Update: Thanks for all the responses. I feel thoroughly educated.
gpt
There are a number of legal issues regarding employment of teenagers (especially in California, where many works are filmed) that can make it very difficult and inconvenient to use them in a production.