The reason why some states put the level so low is because you shouldn't be driving after any drinks, period. Your argument that 'being slightly over the limit

The reason why some states put the level so low is because you shouldn't be driving after any drinks, period. Your argument that 'being slightly over the limit is often safe' does not work, because it relies on people being able to rationally judge how good they are at driving while drunk. Which, as it turns out, generally does not work and leads to accidents. And even if there's 'no one around', that relies on a judgment call made while drunk and impaired. If you told a lawyer 'Sorry, I didn't think anyone was around when I drunkenly drove into them', you'd be laughed out of court and straight to jail. Which is why they're illegal. If you drink and drive, you've established that you're putting yourself and others at danger while driving. The same can be true of driving sleepy, but that also happens at a far less rate statistically than driving drunk in the US.