Every few years some government weenie wants to put breathalyser interlocks in all cars.....
"when the technology is mature."
I design a standards approved breathalyser in the mid 90's using a platinum acid fuel cell.
They won't work because
1- Not reliable enough (Imagine being stranded because the interlock broke)
2- Requires at least annual recalibration (Infrared and Fuel cell based)
3- Someone else can blow in them or make a breath simulator to blow for them.
4- Expensive.
5- Car manufacturers will lobby not to comply (because of 1,2,4)
6- People will rightly complain of government overreach.
The problem is solved through policing, fines, education and making DD cultural poison.
I firmly believe that alcohol interlocks are not useful, solely for reason #3... Here in the UK they're only given to the worst offenders and even then, only marginally effective.
However breathalysers in the hands of the police are a very effective tool. Australia had a huge drink driving problem in the 90's until the police started cracking down on it. You're right that they need regular calibration but this is taken care of by professionals as a failed or out of date calibration certificate is grounds to have every ticket issued by that machine invalidated.
People complain about government overreach but in most countries, breathalysers in the hands of police do the opposite. It forces the burden of proof to be higher for the police. No longer can a cop say "I smelled liquor on his breath you honour" and not have it questioned, now they have to provide the test results, calibration certificate and supporting documentation (and knowing a few Australian defence lawyers, problems with the documentation is how you'll get off a DUI ticket if you really need to). In Australia, which is still quite lax compared to Europe, if you blow under 0.08 they'll usually let you sit on the side of the road for half an hour or so and test you again. At that point you have the option of a urine or blood test, most don't as it will often have a higher reading than the breathalyser so most opt to cop the punishment (do the crime, do the time as we say in Oz).
The flip side of this is that if I haven't been drinking, there is no way for the officer to claim I had. Even if the machine gives off a false reading I can still opt for a urine or blood test (which is done by a medical lab, not the police). If you blow under 0.05 BAC it's a case of "on you way sir", even if you blow 0.049.