Because it's too competitive.
California Interscholastic Federation
Interscholastic sports is defined as athletic competition between multiple academic institutions (or schools).
University Interscholastic League. That's only the abbreviation, I don't know what it is.
Interscholastic was created in 1999.
Interscholastic is an adjective.
University Interscholastic League was created in 1910.
Arizona Interscholastic Association was created in 1925.
California Interscholastic Federation was created in 1914.
Interscholastic League of Honolulu was created in 1909.
Interscholastic Hockey League was created in 1998.
It's a safeguard to ensure sports does not interfere with their education. At least that's the thought behind it.
Sussex County Interscholastic League was created in 1976.