1)They look as cool as can be.

2)They do eliminate gassing, so they will not fade when they get super-duper hot. If you are the king of person who cannot touch your front wheels after you drive, you will benefit from drilled rotors.

3) They sell. They are a racing part for a street car. People always love that. Wings don't work under 90mph, but people people buy them and swear they work. The look of a 6 piston caliper, a thin spoke wheel, kind of needs a drilled rotor to look good. That is why they do it. The performance difference is nill unless you abuse your brakes similar to a racing. They are mostly for aestetics in DOT vehicles.