It's very relevant because as we get older we mature in knowledge, understanding, and wisdom -- that is, if we are paying attention, and seeking to improve ourselves, learn important things, etc. These types change for the better and realize that our younger selves were very ignorant. It's kind of like when you're a really young kid and can't understand why your parents place certain restrictions on you and you only see it as mean or oppressive but then you get older and have children of your own and realize your parents were right (obviously not all parents are good but that's not the point of the example).
It's why governments place age restrictions on those who can serve in office because young people have not yet had enough time to learn how the world really works and it would be dangerous to give them power and authority.
It's proven science that messages, ads, music, media, and things of this nature have an influence on people and not just the young but in most cases people of all ages. Young people are especially prone to fall victim to various sorts of programming and messages because they have not yet developed the cognitive ability to not be influenced by them. If this wasn't true you would not have such things as ads, campaigning, promotional events, etc.