The good reason not to install a breathalyzer in every car is that I don't drive drunk and would vote against any politician foolish enough to suggest something so intrusive.
You don't drive drunk, but other people do. breathalysers are only put in AFTER an offense. To eliminate the "first generation" drunk driving accidents would require preemptive installation of breathalysers on every car.
The way they are implemented now would be similar to only installing seatbelts in cars where the driver has already been in an accident. Similar sentiment was around when seatbelt laws were put in place, "I'm a good driver." but the seatbelt protects you from yourself crashing as well as when someone else crashes into you!
In the same way, breathalysers (ignition interlocks) for everyone wouldn't be "for you" as much as for everyone to prevent them from drinking and crashing into you.
I hadn't thought about widespread ignition interlocks, and obviously there would be a lot of public pushback, and it would be quite intrusive, but I could see it helping reduce traffic fatalities dramatically.
I don't care how much it would reduce traffic fatalities. I am absolutely opposed to this level of nanny state overreach. And I trust that enough other Americans agree with me to prevent this kind of nonsense from making it into law.
What I would support is a further reduction in the allowed BAC, and stricter enforcement of traffic laws in general.
If you don't drive drunk, what do you lose from starting the engine via breathalyzer, rather than via key turn? Why is one more intrusive than the other? Most governments already require you to carry insurance, have a license/training to drive, wear seat belts -- in what way is this different?