Here's why:
* The Super Rod was introduced in Generation VI, but only in Pokemon X. It's used to catch rare Pokemon in specific areas, and it was exclusive to the X version.
* Pokemon Y doesn't have the Super Rod. You will find the Good Rod in Pokemon Y, which is an earlier version that catches fewer Pokemon.
You'll need to trade with someone who has Pokemon X or find a way to access the Super Rod through other means (like a glitch) if you want to use it in your Pokemon Y game.