To give the parent to your comment some benefit of the doubt, some vehicles do have mandatory breathalysers fitted, but as far as I'm aware it's only commercial vehicles in certain sectors of the market (some buses and coaches, I know of, it's possible they're required somewhere in goods transport vehicles)

Some countries already allow convicted DUI to keep driving with aftermarket breathalyzers. IMO in some cases it's good as an optional replacement for the license suspension. If someone depends on their license that may be a good compromise to both not ruin someone's life and ensure public safety.

What about in addition to license suspension?

The suspension as punishment, the breathalyser as prevention of future incidents.

Yes that doesn't address the 'depending on your license' angle. but I'm not sure that should be a valid defence anyway?

Shall we demand hackers to never touch network-connected computer as prevention of future incidents?

I don't think life-long sentences is OK for all but most severe crimes. And a single DUI, especially on lower end of punishable spectrum, is not such.