&gt;I&#x27;m not sure why anyone cares more about why someone is impaired than they do about whether someone is impaired.<p>It&#x27;s easy to target people who are engaging in unnecessary actions at the expense of driving capability. Drinking, using drugs, and texting fall under this category. People are much less accepting of punishments for things seemingly outside of personal control. Imagine the embarrassment for law makers when some mothers&#x27; advocacy group attacks them for banning all new mothers from driving (except those rare exceptions who function well on &lt;4 hours of sleep.) Or the backlash for hardworking people getting arrested regularly because their multiple jobs keep them from getting an amount of sleep that makes driving permissible.