[NEPA_COOPER_S]

The main reasons for drilled rotors are to dissipate Heat, Gas build up and water removal in wet conditions. Gas build up not so much a problem anymore due to pad materials that are used now but every little bit of benefit these holes add help in breaking performance

I have only ever heard that drilled brakes are just for show,
Vented discs do a much better job at cooling due to air being passed over the whole surface continuously where as all drilled brakes do is remove surface area for the pads to work effectively reducing braking performance.