> If they were to catch and jail just 1% of license-less drivers, in a visible way, it would be a deterrent to the other 99%. But the rate of being caught & punished is negligible (at least in the states I've lived in) so people know they'll get away with it.

1% is actually negligible, and would not have a deterrent effect. In fact I wouldn't even be surprised if the effective prosecution rate was somewhat higher than this already.

> I previously lived in a country where the cops set up random roadblocks to check everyone's license & registration and look for signs of intoxication.

I live in a country (France) where this is still the case, and where driving crimes are the second source of jail time after drug trafficking, yet alcohol is still the #1 cause of death on the road, and an estimate 2% of people drive without a license after having lost it (and are responsible for ~5% of accidents).