Everyone has their own path, a person might have a lot of challenges and obstacles to overcome and lead them
to becoming more mature by their experiences. Then it could be partly down to upbringing and even what their main influences were at a younger age etc
Eventually even if its later years the maturity could just happen as a result from a difficult time, a health issue, a loss of someone, a partner, a new job, a baby etc etc
But some might not ever change and they will stay as they are until the end!