Because they don't but its a boring argument so lets not have it.
Basically it runs along the lines of:
The technology was invented/used elsewhere first.
The application in F1 is too specialised, complicated and sophisticated to ever trickle down to the neighbours Hyundai.
The amount of R&D done in F1 teams as a % of that done by the suppliers and the car industry in general is stuff all.
That whenever good technology appears it gets banned anyway.
That all it ever does is make shit fashionable, not possible. So your shiney new Mazda 3 has flappy paddle gear shifts (Sadly not a dual clutch manual but on an auto), fake carbon fibre trim everywhere and still sells off the back of its pharken facebook connectivity.
Then someone says what about aero my car has aero, F1 has aero therefore they are the same and one follows the other. Add in a couple of facepalm jpegs and that's about it, really.
So anyway back on topic. How rubbish is Homo?