Why don't we just install IID/breathalyzers into every car?
Because you can't punish the innocent.
Consider it a safety feature like seatbelts, air bags, or the computer chips that help you steer or brake in emergencies.
If you don't try to drink and drive.... you're innocent and you get to start your car. How many deaths/accidents would we prevent if every car on the road had this safety feature?
Wouldn't most of you sleep better at night with your children or spouse on the road, knowing the chances of a drunk driver killing them is very very slim if every car had one installed?