4 connectors?

The cd player in my truck started acting up, so I figured I would replace it. The new wiring harness has two connectors. I pulled the radio out and find four connectors in the back. I assume the new radio will work satisfactorily, but what are the other two connectors for?

Wasn't thinking--obviously steering wheel controls are part of the reason. Still seems like a lot of wires. I didn't count, but there are probably a couple dozen.