Why are some teenagers and people in their 20s so immature?

As the measurement of maturity is most often linked to a persons responsibilities and how they deal with them, I feel that I should point out, like Andres has, that your grandparents as young adults likely saw healthier economic times. My grandfather payed his way through medical school with a job at Sears. The American ''nuclear family'' ideal is no longer realistic, and our quality as adults should not be held up to that standard of measurement.