Possible reason the controller was sent to Earth

[vikingjedi]

The story we've been given is that Jor-El sent it to Earth to control Clark. That makes no sense UNLESS Jor-El is Zod

If you can control Clark, you can control the FOS. Zod needs the FOS to escape the Phantom Zone

[colonyofcells]

Maybe Jor-El sent the controller to help in Clark's toilet training.