Yes, sometimes ambulances are not very convenient - but if I had a choice of a person having to waste a few hours because ambulance took them to wrong hospital vs them driving quickly while drunk and nervous, I would choose former. I am sorry, your convinience is not worth the extra risks to bystanders.
A vehicle that has the potential to not operate either due to false positive or not handling a legal exception that a lot states have on their books. Is not a vehicle you want to rely on for emergencies. It even becomes more risky if one lives in area that does not have responsive emergencies services.
This is even before we consider possible privacy issues and concerns depending on how this is implemented. Let alone legal and moral considerations of essentially monitoring and scanning of people who have not committed a crime to try and prevent some people from breaking the law.
For example, even in places where emergency services are usually good, Covid peaks strained their capacities quite seriously.
The same can happen during a mass casualty event. If a plane crashes with a lot of survivors, there may not be an ambulance available for your spouse who just went down with a heart attack.
It's restricted because in aggregate or when done repeatedly it would be a disaster (particularly when drunk driver A interacts with drunk driver B), not because doing it once in an emergency would be problematic.
Citation: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3433627/
(at 0.08% BAC fatal accident risk is 13x - what's the risk of waiting ten minutes for an ambulance if your friend is dying?)