If everything is fair and you’re not gaining an advantage then why holdback?
If everyone has to play older kids in high school anyway then why holdback?
The reason is because you are gaining an advantage!!
Let’s say you play JV as a freshman, you are the age of the Sophomores!
As a sophomore on JV you are the age of a junior.
As a junior on Varsity you are the age of a senior.
As a senior on Varsity you are the age of a College Freshman.

You just played 4 years and never played against anyone older than you!!!!!!!!