I'm 29 so maybe I'm too young for this statement but if you ask me it's because younger celebrities tend to be the result of nepotism and don't have any actual talents.
The nepotism part has always been true, and talentless celebrities have been around as long as the concept of "celebrity" has, but the category of celebrities "being famous for no reason" did not truly exist until Paris Hilton. Princesses and Kings aren't "celebrities".
Definitely. We still have that to this day, such as the Kardashians. At least with the Internet some people become famous without those moneyed connections but those are still the exception.