Here's why:
* Collective nouns refer to a group of people or things considered as a single unit.
* While "youth" can refer to a single young person, it more commonly refers to a group of young people as a whole.
For example:
* The youth of today are more tech-savvy than previous generations. (Here, "youth" refers to a group of young people.)
* The youth is our future. (Again, "youth" refers to a collective group.)
Let me know if you'd like to explore other types of nouns!