I believe there are few things people love about youth.
Marketers view the demographic of age 18-49 to be the future. They are also more inclined to spend money on frivolous things.
Where as older people become more conservative with spending as they prepare to retire. They typically aren't "impulse buyers".
Another factor is health and beauty are associated with youth.
More people wish they were age 25 than they do age 55 or above.
They nostalgically recall being able to party all night and recover the next day or do repetitive motion without becoming sore. They had more energy and were more optimistic. Age and wisdom has a way of making us cynical. Most people also don't care for watching their body change over time, wrinkles, laugh lines, grey hair or losing hair, saggy skin, changes in posture, unable to do activities at the level they once did. Everyone is seeking that magic pill/youth serum.
Our culture spends Billions of dollars per year to look younger. Although age discrimination is against the law employers still have ways of discriminating against older job applicants.
"Seeking bright recent college grads to work in high energy office. Most be enthusiastic & enjoy multi-tasking. Experience 0-3 years."
In other words: "Old farts need not apply!"
All of a sudden having "more experience" disqualifies someone. hmm