[jl6]

This idea that 25 is the true age of maturity... is it possible that the thing that makes a 25 year old mature is having had 7 years of adult responsibilities?

If we set the age of adulthood to 25, maybe people won't be mature until 32.

[nomel]

This is biological maturity, as in when the brain is done forming. But, to your point, I wonder how much of that formation is guided by “soft” constructs like social maturity. Assuming it was delayed, maybe you end up with a different brain formation.

[HKH2]

The brain physically reaches maturity at around that age. From memory, the last place to finish development is the prefrontal cortex (where decision making occurs).