Even under check-stop programs, no one can be asked to blow into a machine unless the police officer has reasonable grounds to force you to do so. These grounds must be proven within a court of law.
This is a slippery slope that could be extended and used as a basis for unlimited search and seizure without probable cause.
We could eliminate unpunished crime completely. Seriously. Require every person to be implanted with a GPS chip and micro cameras to record their every action and location. The technology is either there, or not far off. We could monitor and recall every action of every person in the country.
What do you have to hide? If you break the law, you're caught. Your car would be equipped with a monitoring device so that everytime you break the speed limit (by even 1 km/h) your bank account is automatically debited the cost of the ticket. This technology certainly exists. Don't like it? Don't speed.
Toilets could be created that would analyze your urine on every flush. You'd have to have your finger on the pad to pee, and then if you're found to have any illegal substances in your blood, you'd either be fined instantly, or arrested and sentenced automatically. Sounds nuts? Don't think it couldn't happen.
Laws could be come absolutes, with punishments meted out without a justice system. Behaviour could be strictly controlled and crime would become rare and never unpunished.
But, who makes the laws? In a democracy, we face mob rule. True democracy ignores the rights of any minorities and combine it with the system of legal enforcement as stated above, and we're treading in some very dangerous waters. As an example, homosexuals make up 1-10% of the population depending on the stats you read. It would be simple to make homosexual behaviour illegal, and completely enforceable.
Look at "the war on drugs." Why is pot close to becoming legal? Because we can't really stop people from using it. This happened with alcohol previously. But, with the tools of no-Charter-of-Rights democracy and 100% monitoring "for public safety and the abatement of crime" we could finally win that war on drugs, alcohol, or whatever the mob found to dislike.
The elimination of criminal behaviour has always been a problem, not only from the standpoint of ceasing it, but also in figuring out what exactly it is. The freedom from random searches is one tool in finding a balance in that process.