Here's why:
* Shiny Gold is a ROM hack: It's a fan-made game based on Pokemon Gold, and doesn't have the same items or features as the original.
* Super Rods are introduced later: The Super Rod was first introduced in Generation III games (Ruby, Sapphire, Emerald), so it wouldn't exist in Shiny Gold, which is based on Generation II.
Instead of a Super Rod, you can use the Good Rod in Shiny Gold to catch rarer fish. You can find the Good Rod in the following locations:
* Goldenrod Department Store: After winning the Bug Catching Contest, you can buy the Good Rod from the department store.
* Blackthorn City: You can find the Good Rod in the house next to the Pokemon Center.
Good luck catching those rare fish!