Why most younger people(18-30 age range) are usually so less tolerant of my childish behavior compared to middle aged and old people?

I have always noticed that middle aged and old people don't care much and are more tolerant to my childish behavior and behave nice to me and say me politely to act more matured whereas the younger ones especially in my age range(18-21) usually lose patience easily because I act immature and silly and they end up ignoring me or being rude to me. Why is it that way?