I don't think it's the age... I think it's the message. When people hold you in some sort of high esteem, they'll pay attention to you. When you have some bit of status or knowledge they desire, they'll seek you out or listen. Simply put, they have to want to hear what you're saying. The coincidence lies in the fact that age groups generally have different interests.
I used to struggle to communicate my passion for all things cycles to anybody who would listen.... only to find out later in life that the people who want to listen will ask you if they're ready to hear it. Something about leading horses to water, I'm sure. Or maybe the old Murphyism "If you try to please everyone, no one will like you.".