Yellow Peril is probably right.
It's cheaper to produce a wiring loom that has capability of connecting every possible feature/upgrade available on the car model. I can't really tell what this exact connector is used for though.
It's almost always possible to fit an after-market cruise control. If you want the 'original' Stilo cruise control, then that should be possible too, though I'm not sure if it's something you can do yourself easily.